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1. WO2010007443 - METHODS OF DETERMINING PROPERTIES OF LATENT FINGERPRINTS

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

METHODS OF DETERMINING PROPERTIES OF LATENT FINGERPRINTS

The present invention relates to the detection of at least one property associated with a latent fingerprint by selective removal of a latent fingerprint from a substrate on which it has been deposited. The present invention further relates to methods of removing constituents of latent fingerprints from surfaces for analysis. Also included in the present invention is a kit for selectively lifting latent fingerprints from surfaces, as well as other subject matter.

BACKGROUND

Fingerprints are used for identification purposes. As part of established protocols used worldwide, latent fingerprints are generally located at crime scenes via application of dusting agents or suspensions of these particles onto surfaces. Latent fingerprints are formed on surfaces when a person touches the surface. The tips of a person's fingers contain perspiration from pores on the ridges and oils obtained from oily areas of the body such as the face. The grooves between the ridges have no pores. When a person touches an object, the sweat and oils at the ridges of the fingertips are deposited on the surface of the object in a pattern that is identical to the pattern of ridges. The sweat, which is 98% water (at least for eccrine type secretions), evaporates and the oil and sweat residue remains on the surface of the object, thus forming a latent fingerprint with distinguishing patterns.

Dusting agents are usually applied using brushes, or for magnetisable formulations, using magnets which are often termed "magnetic wands". For suspensions, application can be via brushes wetted with the suspension or via a spray of droplets containing the suspension and directed onto the surface from a spray gun. In both cases, the agents contain small particles that selectively adhere to constituents of the prints, producing a pattern corresponding to the pattern of ridges that are unique to the donor of the print.

It is general practice to photograph the developed print which then serves as a record of the print's details. It is also common practice to also lift the developed print from the surface onto a transparent tape so that the print's pattern can be retained and used as evidence together with the photographs of the print. The lifting tape consists of either a roll of transparent plastic tape that has one adhesive side or as a small sheet of transparent plastic with one adhesive side that is supplied stuck to a more rigid plastic backing. The former is used by unpeeling a portion of the tape and tearing or cutting this section which can then be applied, adhesive side down, onto the pre-developed latent fingerprint. In the latter case, the upper transparent side of the tape is peeled from the backing and this is placed, adhesive side down, onto the pre-developed tape.

The material from the print is transferred onto the adhesive surface of the applied tape by gently rubbing the outer surface of the tape, and the tape is then carefully peeled from the surface. In order to protect the freshly exposed sticky surface and the lifted print, a transparent sheet of plastic is placed over the sticky surface covering the lifted print.

There are a variety of commercial tapes available for lifting pre-developed prints and forensic scientists choose tapes according to their particular needs at the scene of crime and their personal experiences.

BRIEF SUMMARY OF THE DISCLOSURE

The present invention relates, at least in part, to a method for obtaining at least two lifted fingerprints from a single latent fingerprint which can be used as evidence and for interrogation to determine additional properties of the fingerprint. Thus, embodiments of the present invention enable a single latent fingerprint to be used both (i) to identify a subject to which the latent fingerprint belongs and (ii) to identify one or more constituents of the fingerprint by interrogating the resulting lifted fingerprint using a mass spectrometric technique.

The present invention may have utility at, for example, a scene of a crime at which a latent fingerprint has been deposited. The method may therefore provide a set of lifted fingerprints for use as evidence, and a second set of lifted fingerprints for direct interrogation of the print by Surface-Assisted Laser Desorption/lonisation-Time of Flight-mass spectrometry (SALDI-TOF-MS) or equivalent MS techniques including those that operate at ambient atmospheric pressure.

The present invention further relates to methods for analysing constituents of a latent fingerprint comprising multiple application of a fingerprint developing agent to a latent fingerprint.

In a first aspect of the present invention, there is provided a method for determining at least one property of a latent fingerprint deposited on a substrate, comprising:

(a) contacting the latent fingerprint with an adhesive surface of a first lifting element, to form a first lifted fingerprint on the surface of the first lifting element; and subsequently

(b) contacting the latent fingerprint with an adhesive surface of a second lifting element to form a second lifted fingerprint on the surface of the second lifting element.

In one embodiment, the method comprises applying pressure to the first lifting element following contacting the latent fingerprint with the first lifting element. In one embodiment, the method comprises applying pressure to the second lifting element following contacting the latent fingerprint with the second lifting element.

In one aspect of the invention, there is provided a protecting element for covering a lifted fingerprint situated on a surface of a fingerprint lifting element, the protecting element comprising a rigid top panel and a wall portion which extends along the perimeter of the rigid top panel, such that the wall portion forms a continuous perimeter. In one embodiment, the rigid top panel of the protecting element, when a lower edge of the wall portion is in contact with the surface of the fingerprint lifting element, does not contact the lifted fingerprint, thus protecting the lifted fingerprint. Thus, when the protecting element is placed over the lifted fingerprint and the lower surface of the wall portion is in contact with the surface of the lifting element, the roof panel is positioned above the lifted fingerprint.

In one embodiment, the protecting element further comprises means for securing the protecting element to the fingerprint lifting element. In one embodiment, the securing means comprises at least one strip of adhesive material adjacent the wall portion. In one embodiment, the protecting element comprises a plurality of adhesive strips. In one embodiment, the protecting element is substantially formed from plastic. In an embodiment, the protecting element is sized so as to ensure substantially all the lower surface of the wall portion is in contact with the surface of the fingerprint lifting element. In one embodiment, the protecting element is substantially square. In alternative embodiments, the protecting element may be rectangular or circular, for example.

In a further aspect of the invention, there is provided a kit for determining at least one property of a latent fingerprint deposited on a substrate, comprising: (a) a first lifting element which comprises an adhesive surface and which is capable of lifting a portion but not all the latent fingerprint;

(b) a second lifting element which comprises an adhesive surface and which is capable of lifting substantially all the latent fingerprint; and (c) a fingerprint developing agent.

In one embodiment, the first lifting element has a lower adhesive strength than the second lifting element. In one embodiment, the first lifting element is an adhesive tape or a gel. In one embodiment, the second lifting element is an adhesive tape, an adhesive sheet or an adhesive gel.

In a further aspect of the invention, there is provided a kit for determining at least one property of a latent fingerprint deposited on a substrate, comprising: (a) a lifting element which comprises an adhesive surface; (b) a first fingerprint developing agent and

(c) a second fingerprint developing agent, wherein the second developing agent is capable of adhering to one or more constituents of the latent fingerprint.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in more detail below, with reference to the following accompanying figures:

Figure 1 ; Spectra of a print applied directly to a stainless steel Matrix-Assisted Laser Desorption/lonisation-Time of Flight-Mass Spectrometry (MALDI-TOF-MS) target plate (Shimazu) and dusted with ROAR Black magnetic powder

Figure 2; Spectra of a blank MALDI-TOF-MS plate

A comparison between Figures 1 and 2 clearly shows the MS peaks due to fingerprint constituents.

Figure 3; Spectra of residues of dusted prints remaining on the surface of the stainless steel target plate following the first lifting of the print (from figure 1 ) with three types of lifting tape; upper Commercial 1 (low adhesiveness), middle Commercial 2 (medium adhesiveness) , lower Commercial 3 (high adhesiveness)

It will be noted that highest intensities of peaks are seen with the upper trace (using tape of the lowest adhesiveness) and lowest in the lower trace (using tape of the highest adhesiveness).

Figure 4; Spectra of dusted prints transferred onto lifting tapes from the surface of the stainless steel target plate (from figure 1 ) with three types of lifting tape; lower Commercial 1 (low stickiness) , middle Commercial 2 (medium stickiness) , upper commercial 3 (high stickiness). SALDI-TOF-MS is performed on the sticky upper surface of the lifted tape which is fixed onto a clean target plate to ensure that the tape is uniformly flat across the plate's surface.

Lowest signal intensities are seen for the lower trace and highest signals for the upper trace. Higher amplification for the lower and middle scans results in interference with low intensity peaks at 413 and 429 mu from the plate (see Figure 2). These are not seen in the upper trace.

Figure 5. Spectra of dusted prints transferred onto lifting tapes from the surface of the stainless steel target plate following first lifts with the three Commercial tapes as before, re-dusting of the residue left on the surface of the metal plate with ROAR Black magnetic powder, lifting of this print with Commercial tape 3 (high stickiness). The lower trace is for the first lift with Commercial tape 3 (highest stickiness), middle trace first lift with Commercial tape 2 (medium stickiness) and the upper trace is for first lift with Commercial tape 1 (lowest stickiness)

Peaks of lowest intensity are seen in the lower trace where the first lift was with the stickiest tape (commercial tape 3). Hence the use of tape of high stickiness is not recommended for the first lift as little residue is available for the second lift and hence poorer spectra are obtained.

Figure 6. Spectra of dusted prints transferred onto lifting tapes from the surface of the stainless steel target plate following first lifts with the three Commercial tapes as before, re-dusting of the residue left on the surface of the metal plate with ROAR Black magnetic powder, lifting of this print with Commercial tape 1 (lowest stickiness). The lower trace is for the first lift with Commercial tape 1 (lowest stickiness), middle trace first lift with Commercial tape 2 (medium stickiness) and the upper trace is for first lift with Commercial tape 3 (highest stickiness).

In all three traces little detail is observed of peaks associated with fingerprint constituents compared with previous figures, indicating that the second lift with the tape of low stickiness is not lifting the residual material from the fingerprint effectively. The new peaks at 413 and 429 may be due to the adhesives in this tape (which can be transferred onto the target plates during the transfer process- see Figure 2).

Figure 7; shows a protecting element of embodiments of the invention.

DETAILED DESCRIPTION

In a first aspect of the present invention, there is provided a method for determining at least one property of a latent fingerprint deposited on a substrate, comprising:

(a) contacting the latent fingerprint with an adhesive surface of a first lifting element, to form a first lifted fingerprint on the surface of the first lifting element; and subsequently

(b) contacting the latent fingerprint with an adhesive surface of a second lifting element to form a second lifted fingerprint on the surface of the second lifting element.

In one embodiment, the method is for determining at least two properties of a latent fingerprint. It will be understood that the term "fingerprint" includes reference to a partial print and/or to prints of other body parts. A latent fingerprint means an impression left by friction ridge skin on a surface or substrate, regardless of whether it is visible or invisible at the time of deposition. As used herein, the term "latent fingerprint" may also include material associated with the impression e.g. one or more developing agents, as described below.

In one aspect of the invention, there is provided a method for determining at least one property of a latent fingerprint deposited on a substrate, comprising: (a) applying a first developing agent to the latent fingerprint; (b) applying a second developing agent to the latent fingerprint; and

(c) contacting the combination of the latent fingerprint, the first developing agent and the second developing agent with a lifting element to form a lifted fingerprint.

In one embodiment, the second developing agent is suitable for use as a matrix agent in a matrix-assisted mass spectrometry technique. In one embodiment the second developing agent is capable of binding to one or more constituents in the latent fingerprint. In an embodiment, the second developing agent is a silica particle, e.g. a hydrophobic silica particle as described herein.

In one embodiment, the method comprises identifying one or more constituents of the lifted fingerprint e.g. using a mass spectrometric technique as described herein.

A "lifted" fingerprint is a fingerprint comprised of material which has been transferred from a fingerprint, e.g. a latent fingerprint which has been deposited on a substrate, to a second surface. The present invention provides for the transfer of fingerprint material from a latent fingerprint to an adhesive surface of a lifting element. In one embodiment, the term "lifted fingerprint" refers to residues of a latent fingerprint which have been transferred from the surface on which the latent fingerprint has been deposited. A lifted fingerprint need not necessarily show the pattern of a fingerprint and may be comprised of the constituents making up the fingerprint, which are described in detail later.

The present invention relates to, at least in part, the sequential transfer of fingerprint material from a single latent fingerprint to at least two separate substrates. The first transfer may be to obtain a lifted fingerprint which is of a visual quality that is sufficient for use in identification purposes. The first transfer preferably does not remove all of the material associated with the latent fingerprint so that a second transfer of fingerprint material may be carried out. The second transfer may be used to obtain a second lifted fingerprint which can then be interrogated using a mass spectrometric technique so as determine at least one constituent of the latent fingerprint. In one embodiment, the present invention involves the use of at least two lifting elements, the first of which is used to transfer some but not all of the material associated with the latent fingerprint such that sufficient material is not removed from the latent fingerprint so that a second lifting element can be used subsequently to transfer substantially all of the remaining latent fingerprint.

In one embodiment, the method includes interrogating a sample. It will be understood that the terms "sample" and/or "analyte" in the context of the present invention can be taken to mean a print, a sample taken from a print and/or which includes materials taken from a latent fingerprint and which includes e.g. constituents of a latent fingerprint.

In one embodiment, the surface of the first lifting element has an adhesive strength which is equal to or less than the adhesive strength of the surface of the second lifting element. In one embodiment, the surface of the first lifting element has an adhesive strength which is less than the adhesive strength of the surface of the second lifting element.

In an embodiment, the adhesive surface of the first lifting element has an adhesive strength such that, upon contact with the latent fingerprint, the first lifting element is capable of removing some but not all the latent fingerprint, thereby leaving a portion of the latent fingerprint remaining on the substrate.

Thus, the first lifting element has an adhesive strength which removes some but not all of the material associated with the latent fingerprint. The first lifting element should be able to transfer enough material from the latent fingerprint to the adhesive surface to produce a lifted fingerprint which is suitable for identification purposes. Thus, the first lifted print should comprise sufficient material from the latent fingerprint to identify the fingerprint pattern without removing so much material that a second lifted fingerprint cannot be produced. The term "portion" as used in this context therefore relates to an amount of material from a latent fingerprint which is not all or substantially all of the material making up the latent fingerprint.

In one embodiment, the adhesive surface of the second lifting element has an adhesive strength such that, upon contact with the latent fingerprint, the adhesive surface is capable of removing substantially all the latent fingerprint. In one embodiment, the adhesive surface of the second lifting element has an adhesive strength such that the adhesive surface is capable of removing substantially all the portion of the latent fingerprint remaining on the substrate.

The adhesive surface of the first lifting element may have an adhesive strength such that it is capable of lifting less than 100% of the latent fingerprint and material associated therewith. The adhesive surface of the first lifting element has an adhesive strength which is capable of lifting less than 90% of the latent fingerprint, e.g. 85%, 80%, 75%, 70%, 65%, 60% of the latent fingerprint e.g. less than around 50% of the latent fingerprint and material associated therewith.

In one embodiment, the adhesive surface of the second lifting element has an adhesive strength such that the adhesive surface is capable of lifting at least 50% of the latent fingerprint or portion of latent fingerprint remaining following contact by the first lifting element. In one embodiment, the second lifting element is capable of lifting at least 60%, e.g. 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the latent fingerprint or portion of the latent fingerprint.

The first lifting element and the second lifting element are independently selected from a tape and a gel. In one embodiment, the first and/or second lifting agent is a magnetisable particle. In one embodiment, the first and/or second lifting element may be a magnetisable particle. In one embodiment, the second lifting element, which is used to obtain a lifted fingerprint for use in a mass spectrometric technique, is a magnetisable particle. In one embodiment, the lifting element is a silica particle as disclosed herein in relation to developing agents. Such particles may also be used as lifting elements. The particles may be applied to the latent fingerprint for example in a powder or suspension using a magnetic wand. If the particles are applied in powder form, the method further comprises a step of applying a solvent to the powder on the latent fingerprint so as to solubilise the residue constituents. The particles and the fingerprint constituents adhered thereto may be removed from the surface by a magnetic wand and may then be deposited directly on a surface for interrogation by a mass spectrometric technique. In one embodiment, the method comprises evaporating the solvent prior to interrogation.

In an alternative embodiment, the particles may be applied to the latent fingerprint in a suitable liquid medium. Typically, the liquid medium is an aqueous:solvent mixture. The solvent may be a water-miscible solvent. In one embodiment, the aqueous component is water. The solvent may be for example a water miscible solvent i.e. 100% miscible in all proportions in water. In one embodiment, the solvent is ethanol. The water: solvent ration ranges from about 99.9:0.1 (watersolvent) to about 96:4 (water: solvent). The level of solvent preferably is typically not greater than about 4%, since a higher level of solvent may result in the fingerprints becoming dissolved or their definition reduced. It is preferable to include at least a trace amount of solvent to ensure that the particles, e.g. nanoparticles, remain as discrete particles and do not coalesce to form aggregates.

The first lifting element typically comprises an adhesive surface which can be used to lift a portion of the latent fingerprint from the substrate on which the latent fingerprint was deposited.

In one embodiment, the first lifting element has a lower adhesive strength than the second lifting element. In an alternative embodiment, the first lifting element has an adhesive strength which is equal to the adhesive strength of the second lifting element. Adhesive strength may be measured a number of ways. For example, peel adhesion may be used to determine the adhesiveness of a product. Resistance to peel is determined by measuring the force required to peel away an adhesive element e.g. a tape from a rigid surface. The amount of force needed to remove the element, peeled at 180 degrees at specified speed, yields a value measured in English or metric units. Alternatively, or in addition, sheer adhesion or holding power can be used to determine adhesiveness. Sheer adhesion is characterized as a resistance to flow or movement under stress. Shear is measured by the amount of time necessary for an adhesive element e.g. a tape to separate from a parallel test surface to which it has been adhered. Standard tests for measuring adhesiveness are described by the American Society for Testing and Materials.

In one embodiment, the first and second lifting elements are independently selected from a tape, a sheet and a gel.

Tapes which are suitable for lifting latent fingerprints are commercially available. These tapes can be of differing adhesive strength and therefore lift differing portions of latent fingerprints. Examples of commercially available tapes include for example "Rough Lift" Fingerprinting tape, from Arrowhead Forensics and CSI Flexible tape from CSIEquipment.com. Typically the tape comprises a backing layer and a layer with an adhesive surface onto which a latent fingerprint is transferred.

In one embodiment, the first and/or second lifting element may be a gel. Exemplary gels include those obtainable from CSIEquipment.com.

In one embodiment, the first lifting element has a low to medium adhesive strength. Preferably, the first lifting element has an adhesive strength which is sufficient to lift a latent fingerprint of suitable quality for use as evidence of the latent fingerprint without lifting substantially all the latent fingerprint.

In one embodiment, the second lifting element has a high adhesive strength. Preferably, the second lifting element has an adhesive strength which is sufficient to remove sufficient all the latent fingerprint from a substrate on which it is deposited. Examples of commercially available tapes which have a high adhesive strength include J Lar lifting tape (CSIEquipment.com).

In one embodiment, the second lifting element is suitable for use as a substrate in a mass spectrometric technique. In one embodiment, the second lifting element is a high temperature tape i.e. a tape able to withstand high temperatures without charring. In one embodiment, the second lifting element has a uniform distribution of adhesive over its adhesive surface. In one embodiment, the second lifting element comprises a uniformly flat adhesive surface in order to obtain consistent data on interrogation across the adhesive surface.

In one embodiment, the method further includes contacting an area where there is or may be a latent fingerprint with a first developing agent, prior to contacting the latent fingerprint with an adhesive surface of a first lifting element, thereby forming a first lifted fingerprint on the surface of the first lifting element. The step of contacting the area with the first developing agent may include spraying the area with a suspension which includes the first developing agent. Alternatively, or in addition, the step of contacting the area with the first developing agent may include brushing the area with a powder comprising the first developing agent.

In one embodiment, the method further comprises a step of contacting the latent fingerprint with a second developing agent, after the step of contacting the latent fingerprint with an adhesive surface of a first lifting element and prior to the step of contacting the latent fingerprint with an adhesive surface of a second lifting element to form a second lifted fingerprint on the surface of the second lifting element.

The first and second developing agents are agents which permit the detection and/or imaging of a latent fingerprint and/or one or more constituents of the latent fingerprint.

Application of the first developing agent and/or second developing agent may be by way of a brush. Alternatively, application may be by way of a magnetic wand, and, in this embodiment, the particulate matter is magnetic or para-magnetic. This has health and safety advantages as it reduces any personnel's exposure to particulate matter, particularly via inhalation. Alternatively, the article in which a print is deposited may be immersed in the liquid medium (e.g. suspension of nanoparticles e.g. an ethanoic suspension) and then removed. The length of immersion is not critical and may vary from about 1 minute to about 12 hours or longer.

The method may include the use of a second developing agent. The first developing agent and the second developing agent may be the same agent or different.

In one embodiment, the fingerprint may be contacted by a fingerprint developing agent which can be used to detect fingerprints. Examples of a first developing agent include aluminum, a bi-chromatic powder, a silica particle and Magneta Flake and Commercial White.

In one embodiment, the second developing agent is capable of acting as a substrate in an ionisation-based mass spectrometric technique and may be suitable for use as a matrix agent in a matrix-assisted mass spectrometry technique. In one embodiment, the second developing agent is capable of binding to one or more constituents in the latent fingerprint. Preferably, the second developing agent has properties which enables constituents in the latent fingerprint to stick to the surface of the developing agent, such that, on interrogation via a laser or other ionising agents, ionisation of the full range of constituents within the print occurs, enabling the resulting ions to be identified in the mass spectrometer.

In one embodiment, the second developing agent is selected from a hydrophobic silica particle and aluminium powder.

Details of suitable developing agents are described herein. In one embodiment, the first and the second developing agent are independently selected from a powder which includes silica particles, e.g. hydrophobic silica particles. The particles may be, for example, nanoparticles (< 100 nm in diameter), other sub-micron particles or microparticles. The silica particles may comprise a dye or coloured particle. In one embodiment, at least a portion of the silica particles are magnetic.

In one embodiment of the present invention, the first and/ or second developing agent may comprise hydrophobic silica particles. One class of hydrophobic silica particles is obtainable by reacting together in a single step a mixture of (1 ) silane ether monomers, for example, a alkoxysilane and (2) organically substituted silane ether monomers, for example a phenyl modified silicate, with a hydrolysing agent e.g. an alkali (method A).

Thus, the method typically comprises the use of alkoxysilane monomers. The method may comprise the use of tetraalkoxysilanes (abbreviated herein to TAOS). The TAOS's are particularly selected from TEOS (tetraethoxysilane) or TMOS (tetramethoxysilane).

In one embodiment, the mixture further comprises a water miscible solvent, for example, ethanol, and also water. The method may be carried out at ambient temperature. The duration of the reaction is not critical. The reaction between the TAOS monomers and PTEOS (phenyltriethoxysilane) monomers may be performed overnight or for an equivalent time period, that is to say for between about 12 and about 18 hours. The length of the reaction has an effect on the size of silica particles produced. It is believed that the earlier a reaction is stopped, the smaller the particles which are formed. Therefore, the reaction can be performed over a period of less than 12 hours e.g. between 6 and 12 hours. The reaction may be alternatively performed for longer than 18 hours. If desired, the temperature may be elevated (or reduced) and the duration of the reaction reduced (or increased).

The hydrolysing agent, typically an alkali, acts as a catalyst within the reaction. Preferably this catalyst is a hydroxide, for example ammonium hydroxide. The catalyst may instead be an acid. Examples of acids are mineral acids, e.g. hydrochloric acid. In this method, the reaction comprises an acid induced hydrolysis.

The silane ether monomer, for example a TAOS, and the organically substituted silane ether monomer, e.g. PTEOS monomers may be used, for example, in ratios (PTEOS:TAOS) of from 2:1 to 1 :2 e.g. 4:3 to 3:4 and in particular 1.2:1 , to 1 :1 .2. In one class of methods, the ratio is at least about 1 :1 , e.g. up to 1 :5, for example 1 :2. In one class of methods, the PTEOS:TAOS ratio is preferably 1 :1 v/v. It will be understood that, where one or both of the TAOS and PTEOS are replaced by alternative reagents, the same ratios may be used.

The hydrophobic silica particles produced by the above method tend to be predominantly nanoparticles, that is to say, of an average diameter of approximately 200nm to about 900nm, typically about 300nm to 800nm and particularly 400nm to 500nm. These nanoparticles can be subsequently processed to form microparticles, which can be considered coalesced nanoparticles. The microparticles may be produced using a method which for example comprises the following steps: i) centrifuging a suspension of particles ; ii) transferring the suspension of hydrophobic silica particles into an aqueous phase; iii) extracting the suspension from the aqueous phase into an organic phase ; iv) evaporating the organic phase; and v) crushing and sieving the product obtained in (iv).

The organic phase preferably comprises an organic solvent which is non-polar or has low polarity. The organic phase may be dichloromethane or another organic solvent for example alkanes, e.g. hexane, toluene, ethyl acetate, chloroform and diethyl ether.

Alternatively, hydrophobic silica microparticles can be obtained from a reaction product containing hydrophobic silica nanoparticles using a method comprising: (a) centrifuging the reaction product; and (b) washing the reaction product in a fluid.

The method may comprise repeating steps (a) and (b) a plurality of times. Preferably, the fluid is an aqueous:solvent mixture and is typically a waterorganic solvent mixture. Typically, the organic solvent is ethanol. Preferably the initial fluid comprises a mixture of water and organic solvent at a ratio of from about 60 (water):40 (solvent) to about a 40:60 v/v mixture. In other embodiments, the solvent can be, for example, dimethylformamide, n-propanol or iso-propanol.

Typically, the proportion of solvent in the mixture is increased between the initial washing (i.e. suspension) (b) and the final washing (suspension). To obtain microparticles which are coalesced nanoparticles, the final suspension is dried. The microparticles may then be sieved. Once sieved, the microparticles are ready for application as a fingerprint developing agent e.g. a first developing agent as described herein and/ or a second developing agent.

The microparticles may be considered to be aggregates of smaller silica nanoparticles. In this embodiment, the microparticles are of sufficient size to be efficiently captured using face masks and hence not inhaled. Thus, in one embodiment, the silica microparticles have an average diameter of at least 10 μm, typically at least 20 μm. Typically, the microparticles have an average diameter of from about 30-90μm. In some embodiments, the microparticles have an average diameter of between about 45-65μm or from about 65 to 90μm. Particularly, the first and/ or second developing agent comprising the microparticles may be a dry particulate matter.

In one class of methods, the first and/ or second developing agent comprises hydrophobic silica nanoparticles. Hydrophobic silica nanoparticles can be isolated using a method which comprises centrifuging a reaction product from method A described above and suspending it in an aqueous:solvent mixture. The aqueous:solvent mixture is a first aqueous:solvent mixture and is preferably a 50:50 mixture. The method may further comprise removing the reaction product from the first aqueous: solvent mixture, centrifuging it and suspending it in a second aqueous:solvent mixture. Preferably, the second aqueous: solvent mixture has a similar proportion of solvent and aqueous component as the first mixture. The aqueous solution which forms part of the aqueous:solvent mixture is preferably water. The solvent which makes up the solvent portion of the aqueous:solvent mixture is, for example, a water-miscible solvent, for example ethanol. Alternatively, dimethylformamide, n-propanol or iso-propanol could be used.

The step of suspending the reaction product in an aqueous:solvent mixture may be repeated a plurality of times. Preferably, the composition of the aqueous:solvent mixture is altered to increase the proportion of solvent in the aqueous:solvent mixture over the course of repeated suspensions. Preferably, the method comprises, in a final step, suspending the reaction product in an aqueous: solvent "mixture" which is 0% aqueous:100% solvent. The total number of suspensions is typically from 3 to 10, e.g. 4, 5, 6, 7, 8 or 9. Typically after each suspension except the final suspension the suspensions are centrifuged. The nanoparticles can be stored in the final ethanolic suspension. It will be appreciated that centrifugation is one exemplary method of isolating the nanoparticles from the aqueous:solvent mixture and other separation techniques are not excluded.

In one embodiment, the first and/ or second developing agent comprises hydrophobic silica nanoparticles. One class of the first and/ or second developing agent is a suspension of hydrophobic silica nanoparticles in a fluid. The fluid may be an ethanolic aqueous suspension. Alternatively, other organic solvents may be used in place of ethanol in the suspension e.g. dimethylformamide, n-propanol or iso-propanol.

Alternatively, the first and/ or second developing agent can include hydrophobic silica particles can be obtained using methods in the art, (see for example, Tapec et al NanoSci. Nanotech. 2002. Vol. 2. No. 3 / 4 pp405-409; E. R. Menzel, S. M Savoy, S. J. Ulvick, K. H. Cheng, R. H. Murdock and M. R. Sudduth, Photoluminescent Semiconductor Nanocrystals for Fingerprint Detection, Journal of Forensic Sciences (1999) 545-551 ; and E. R. Menzel, M. Takatsu, R. H. Murdock, K. Bouldin and K. H. Cheng, Photoluminescent CdS/Dendrimer Nanocomposites for Fingerprint Detection, Journal of Forensic Sciences (2000) 770-773).

In one embodiment, the first and/ or second developing agent comprises hydrophobic silica particles into which a dye has been incorporated. In an embodiment, the dye to be incorporated into the particle can be for example a coloured or a fluorescent dye. Examples of dyes included in the scope of the invention are, although not limited to, fluorescein derivatives, for example Oregon Green, Tokyo Green, SNAFL, and carboxynapthofluorescein, rhodamine (e.g rhodamine B and rhodamine 6G) and analogues thereof, thiazole orange, oxazine perchlorate, methylene blue, basic yellow 40, basic red 28, and crystal violet and analogs thereof. Without being bound by scientific theory, it is considered that dyes which are positively charged, for example, rhodamine, are better incorporated when PTEOS is used in the method than dyes which comprise negatively charged anionic groups such as carboxylic groups. Examples of other dyes which could be used in the invention include those which possess a planar aromatic substructure and positively charged functional groups (e.g. ethidium bromide and other DNA intercalating agents).

In one embodiment, the hydrophobic silica particle is embedded with a metal, a metal oxide and/or a carbon, which aids its use as a substrate for matrix based mass spectrometric techniques such as MALDI-TOF-MS.

It may be advantageous for the particles to be magnetic or paramagnetic. For example, magnetisable microparticles can easily be dusted over fingerprints, using a magnetic wand or other appropriate tool. In a preferred embodiment of the invention therefore, magnetic or para-magnetic subparticles are incorporated into hydrophobic silica particles. In an embodiment of the invention, the particles are magnetisable e.g. magnetic or paramagnetic. The magnetic and/or paramagnetic particles may be any magnetic or paramagnetic component, for example, metals, metal nitrides, metal oxides and carbon. Examples of magnetic metals include iron, whilst examples of a metal oxide include magnetite and haematite.

In one embodiment, the carbon is carbon black, carbon nanoparticles, a fullerene compound or graphite or an analog thereof. A fullerene compound is composed of at least 60 atoms of carbon (e.g C60). Preferably the carbon is in the form of carbon nanoparticles. Carbon nanoparticles may be in the form of, for example, carbon nanotubes (derivatized or underivatized). The carbon nanotubes may be multi-walled carbon nanotubes and/or single walled carbon nanotubes.

In one embodiment, the metal oxide is selected from titanium oxide (TiO2), magnetite, haematite and combinations thereof. In an embodiment, the metal is selected from aluminium, iron and combinations thereof. However, it is considered that, in alternative embodiments, the skilled person will consider that alternative metal oxides and or metal nitrides can be used which assist in the ionization process of the mass spectrometric technique can be used in the invention. Similarly, the skilled person will consider that other metals and/or forms of carbon which assist in the ionization process can be used in the particulate matter. The metal, metal oxide, metal nitride or carbon may be embedded within the particles of the particulate matter. The particles preferably have an average diameter of < 100μm, for example a diameter of < 1 μm. In one embodiment, the particles have an average diameter from about 10nm to about 100μm.

The hydrophobicity of the silica particles enhances the binding of the particles to the fingerprint. Thus, in one embodiment, the metal, metal oxide and carbon are incorporated in and/ or embedded in a hydrophobic silica particle.

In one embodiment, the method comprises analysing the first lifted fingerprint to determine a pattern of the latent fingerprint, wherein optionally said analysis is performed using a solid-state fingerprint reader and/or an optical fingerprint reader.

Optical methods may be used, for example, a UV search light, optical scanner including a flat-bed optical scanner, a fluorescent scanner and a UV visible scanner.

In one embodiment, the method comprises a step of identifying a subject who deposited the latent fingerprint by analysing the first lifted fingerprint. The step of identification may include comparing the first lifted fingerprint to one or more fingerprints to thereby identify the subject. The one or more fingerprints used for comparison may be stored in a database.

The methods of the invention may additionally include a step of covering the surface of the second lifting element and the second lifted fingerprint. The method may include applying a protecting element to the second adhesive element such that the protecting element is situated adjacent to but not contacting the second lifted fingerprint. The protecting element may include adhesive outer tapes on its underside so that it can be easily applied to the surface to provide the necessary cover over the raised print. The cover is also sufficiently rigid so that it is raised above the surface of the lifting tape due to the presence of the sticky edging around its perimeter, and its rigidity is sufficient to prevent contact between the underside of the cover and the sticky surface of the lifting tape.

In one embodiment, the method includes detecting, e.g. identifying, one or more constituents of the second lifted fingerprint. The method may include quantification of constituents within fingerprints. The term "constituent" refers to any material which it is desired to detect for, in particular, pre-selected compounds. The constituent is, or may be, within i.e. included in a fingerprint, that is the material which constitutes the fingerprint contains, or is suspected of containing or may contain the constituent.

The one or more constituents may be identified by interrogating the second lifted fingerprint by a mass spectrometric technique. The mass spectrometric technique may be an ionisation-based technique e.g. a matrix associated mass spectrometric technique. Samples prepared according to the methods of this invention may be analysed with any mass spectrometer in which the ionisation technique allows selective ionisation of a sample on a specific region of a surface. Suitable ionisation techniques include, without limitation, matrix assisted laser desorption ionisation (MALDI), surface assisted laser desorption ionisation (SALDI), fast atom bombardment (FAB), secondary ion mass spectrometry (SIMS), desorption electrospray ionisation (DESI), desorption sonic spray ionisation (DeSSI), a direct analysis in real-time (DART) ion source, or an atmospheric solids analysis probe (ASAP).

In MALDI the sample is typically co-deposited with a crystalline matrix material. The matrix agent e.g a solution comprising the silica particles described herein or 2,5-dihydroxybenzoic acid (DHB) is capable of absorbing energy from the laser used in the technique. The photons from laser pulses are absorbed by the matrix molecules, with the energy gained in this process ultimately resulting in desorption and ionisation of the analyte species in the sample, typically generating pseudomolecular ions. MALDI can be used with samples under vacuum ionisation or at atmospheric pressure. SALDI is similar to MALDI, except that rather than using a crystalline matrix, a suspension of a solid in a non-volatile liquid, for example a fine graphite powder in glycerol, is used as the matrix that is mixed with the analyte.

In FAB the material to be analysed is mixed with a non-volatile matrix, generally a liquid with low volatility, such as glycerol, thioglycerol or 3-nitrobenzyl alcohol. The sample is then placed into a vacuum source and bombarded with a high energy beam of atoms generating ions from the sample that can be analysed by the mass spectrometer. The beam of atoms is typically formed from a mono atomic inert gas, such as argon or xenon. SIMS is similar to FAB, but uses a beam of primary ions, such as Cs+, to bombard the sample containing the matrix and analyte, in place of the beam of fast atoms.

Other ionisation techniques commonly used to form ions from a surface for analysis by mass spectrometry utilise atmospheric pressure sources and involve directing various species against the surface to generate ions from the sample. In DESI an electrospray source is used to create charged droplets that are directed at the solid sample. The charged droplets are able to pick up molecules from the sample through interaction with the surface and then form ions from the sample that can be directed into the analyser of a mass spectrometer. In DeSSI sonic spray ionisation is used in place of electrospray ionisation to form the ions that are directed at the sample surface. In DART an excited state gas stream is formed from a gas by glow discharge. The excited state gas atoms or molecules, for example of helium or nitrogen, are then directed against the sample surface, where they interact with the sample to desorb and ionise the compounds it contains, with the resulting ions then directed into the analyser of the mass spectrometer. In ASAP a jet of heated gas is directed at the sample surface and the desorbed species are ionised by corona discharge.

After the ions have been formed in the ion source, they can be analysed using any suitable mass spectrometric analyser. Suitable mass analysers include those based upon time of flight (TOF), quadrupole (Q), magnetic sector (B) quadrupole or linear ion trap (IT), fourier transform ion clyclotron resonance (FTICR) or obitrap technology, or combination instruments such as triple quadrupole, Q-TOF, IT-orbitrap, IT-FTICR. For example, particularly suitable combinations of ionisation technique and analyser are provided by MALDI-TOF, SALDI-TOF, DART-IT or DESI-IT.

In one embodiment, the mass spectrometric technique may be selected from MALDI-TOF-MS and SALDI-TOF-MS.

In one embodiment, the method includes applying the second lifted print, located on the adhesive surface of the second lifting element to sample support e.g. a MALDI or SALDI target plate (sample support) prior to MS analysis.

Typically, a sample support e.g. MALDI-TOF-MS or SALDI-TOF-MS sample support tends to be a plate, for example, a stainless steel plate, which is designed to fit into an MS system. The plate may comprise a well or plurality of wells to which a sample (for example a lifted fingerprint) is added.

In one embodiment, for example if the second developing agent is not suitable as a matrix or substrate for the mass spectrometric technique, the method may further comprises adding a matrix agent to the second lifted fingerprint prior to interrogation.

In one embodiment, the constituents of the fingerprint adhere to the second developing agent such that ionisation of the constituents occurs when the second lifted print is interrogated by the ionisation based mass spectrometric technique. The constituents of the latent fingerprint which may be detected using the method of the present invention include for example (1 ) endogenous residues e.g. cholesterol, squalene and fatty acids (2) contact residues e.g. residues from a narcotic e.g. cocaine and/or residues from ballistics, and (3) exogenous metabolites e.g. nicotine metabolites.

The constituents detected and/or identified by the present invention include (1 ) an endogenously produced substance e.g. proteins, lipids, DNA, peptides and/or endogenously derived metabolites which is present as a constituent included in a latent fingerprint; (2) an exogenous compound or metabolite which is present as a constituent included in a fingerprint; and/or (3) a contact residue which is present on or within a fingerprint.

Examples of the types of constituent include for example (1 ) squalene and cholesterol; (2) cocaine and its metabolites and nicotine and its metabolite and (3) ballistic residues from e.g. firearms and/or explosives, residues from handling drugs of abuse (narcotics) e.g. cocaine.

Other examples of endogenous residues which may be identified by the method include for example endogenous substances (e.g. squalene, cholesterol, waxes and esters, steroids e.g. estrogens and testosterone and markers of gender and health) which may be secreted through skin pores and deposited with other chemicals within the fingerprint. The method may also be used to detect the metabolites and conjugates of the aforementioned. Examples of endogenous residues may also include exogenous metabolites, for example, drug and their metabolites including drugs of abuse and their metabolites, prescribed drugs and metabolites and compounds derived from dietary sources or breakdown products of the same. The method could also be applied to the proteomic or genomic analysis of the cells (e.g shed skin cells) or DNA respectively located within the developed print. The method may also be used to detect other contact residues for example, illegal drugs e.g. narcotics, explosive material, for example, material used in bomb making processes, and residue from the use of a fire arm.

The method of the present invention may be used to analyse a variety of residues which may be found on a fingerprint. Thus, in an embodiment, the method may be used to develop and analyze latent fingerprints from smokers. It is well established that nicotine is extensively metabolised to cotinine in vivo and there is evidence that both nicotine and cotinine are excreted together in sweat. In one embodiment, the method described herein may be used to detect or determine whether a person has handled or ingested drugs of abuse, for example, cocaine.

In one embodiment, at least one endogenous residue and at least one contact residue are co-deposited within the fingerprint.

One class of methods seeks to determine the presence or absence of a predetermined substance. In this case, the mass spectrum is examined for the presence of one or more peaks associated with this known substance. Another class of methods seeks to identify one or more substances in a print by comparing peaks in the mass spectrum with a database or library of peaks.

In one embodiment, the method comprises preparing at least one calibration standard for use in calibrating the mass spectrometric technique. This may be done prior to interrogating the second lifted fingerprint. In an embodiment, the method comprises analyzing the outcome of the interrogation to e.g. determine whether a specific constituent is present in the fingerprint.

Figure 7 shows a cross section of the lifting tape 1 with the pre-dusted lifted latent fingerprint 3 on its sticky surface. A protecting element 5 is shown which comprises a rigid top panel 7. A wall portion 9 is attached to the top panel at an angle. The angle may be from about 30 degrees to approximately 90 degrees, e.g. 40, 45, 50, 55, 60, 65,

70, 75, 80, 85 or 90 degrees. The wall portion 9 has strips of adhesive tape (not shown) around its perimeter so that when it is pressed onto the surface of the lifting tape 1 the lid sticks to the tape and the print 3 is completely sealed by the rigid cover 7, as shown in Figure 7.

In a further aspect of the invention, there is provided a kit for determining at least one property of a latent fingerprint deposited on a substrate, comprising: (a) a first lifting element which comprises an adhesive surface and which is capable of lifting a portion but not all the latent fingerprint;

(b) a second lifting element which comprises an adhesive surface and which is capable of lifting substantially all the latent fingerprint; and

(c) a fingerprint developing agent.

In one embodiment, the first lifting element has a lower adhesive strength than the second lifting element. In one embodiment, the first lifting element is an adhesive tape or a gel. In one embodiment, the second lifting element is an adhesive tape, an adhesive sheet or an adhesive gel, as described herein.

The kit may also comprise an apparatus for applying the fingerprint developing agent to a substrate upon which a latent fingerprint may be present. The apparatus may be selected from a brush and a wand, and may be magnetic. In one embodiment, the kit further includes a protecting element for covering a lifted fingerprint situated on the adhesive surface of the first and/or second lifting element. In one embodiment, the protecting element comprises a rigid top panel. The top panel may be formed from plastic. In one embodiment, the protecting element may comprise a continuous wall which forms a closed perimeter when in contact with the lifting element. The protecting element may further comprise one or more adhesive tabs for securing the protecting element to the lifting element. The one or more adhesive tabs may be adjacent to the wall of the protective element.

The kit may additionally include instructions for use.

Examples Examples of SALDI-TOF-Mass spectra from latent fingerprints from a single donor were obtained using a Shimdazu Axima plus system.

Example 1

A female donor rubbed her index finger across her forehead without prior washing of hands and applied her print onto a stainless steel MALDI plate (Shimazu, Manchester UK) by pressing the rubbed finger on the plate. After a period of 1 hour, the resulting latent fingerprint was dusted with ROAR Black magnetic powder using a commercial magnetic wand (CSI Equipment (Northants, UK)) to gently pass the powder agglomerate on the end of the wand over the surface of the print. Details of the ROAR Black Magnetic powder can be found in for example PCT Application No.

PCT/GB2006/050234 (WO 2007/017701 ) and PCT Application No. PCT/GB2006/050233 (WO2007/017700).

The MS interrogation experiments were performed using a Shimadzu Biotech Axima TOF2 time-of-flight mass spectrometer (Kratos, Shimadzu, Manchester, UK) in positive ion mode. The laser powder was fixed to minimize the laser influence on the results and each spectrum was obtained from 40-750 Da with 80 laser shots. Each sample was analysed four times to check for reproducibility and to avoid artifacts.

The latent fingerprint present on the plate was then subjected to SALDI-TOF-MS and the resulting mass spectra are shown in Figure 1 . As a control, a blank MALDI-TOF-MS plate was also subjected to MALDI-TOF-MS, the spectrum of which is shown in Figure 2.

A comparison between Figures 1 and 2 shows the MS peaks due to fingerprint constituents.

Example 2

Fingerprints were applied directly to the surface of the stainless steel target plate, as described in Figure 1 . The resulting latent fingerprints were dusted with ROAR black magnetic powder as described above. Three types of lifting tape, each with an adhesive surface that differed in adhesiveness between the tapes, were applied to residues of the dusted fingerprints. The tape, sticky side down was carefully applied to the surface to minimise introduction of air bubbles onto the sealed surface. The upper surface of the tape was gently rubbed to ensure transfer of the developed print onto the tape. The tape was then slowly peeled from the surface and immediately applied to the surface of a clean stainless steel MALDI-TOF-MS plate such that the sticky side was uppermost. The lifted tape was attached at its edges to the surface of the plate using commercial adhesive tape (cellotape) so the tape's surface was flat. The portion of the tape carrying the transferred latent fingerprint residue was then subjected to SALDI-TOF-MS.

The results are shown in Figure 3. The upper spectra shows the spectra using a tape with low adhesiveness (Tape 1 ). This tape is pre-cut lifting tape (120mm x 65mm) and is available from CSI Equipment (Northants, UK). The middle spectra shows the spectra gained using a tape of medium adhesiveness (Tape 2). Tape 2 is J-Lar tape, also available from CSI Equipment Ltd (Northants, UK) which is a polypropylene tape with an acrylic adhesive. The lower spectra is obtained using a lifting tape of high adhesiveness (Tape 3). Tape 3 is a high temperature tape (Kapton® polyimide tape) which is widely available (e.g. from KaptonTape.Com)

It will be noted that highest intensities of peaks are seen with the upper trace and lowest in the lower trace. Thus, the tape with the lowest adhesiveness provides the spectra with the highest intensity.

Example 3

Latent fingerprints were dusted using ROAR black magnetic powder. The dusted prints were transferred onto lifting tapes from the surface of the stainless steel target plate (from figure 1 ) with three types of lifting tape, described above in Example 2. SALDI-TOF-MS was then performed on the sticky upper surface of the lifted tape which is fixed onto a clean target plate to ensure that the tape is uniformly flat across the plate's surface.

The results are shown in Figure 4. The lowest signal intensities are seen for the lower trace (high adhesiveness) and highest signals for the upper trace (lowest adhesiveness). Higher amplification for the lower and middle scans results in interference with low intensity peaks at 413 and 429 mu from the plate (see Figure 2). These are not seen in the upper trace.

Example 4

Fingerprints were applied to the surface of a stainless steel target plate as before. The resulting latent fingerprints were dusted with ROAR black magnetic powder as before. The dusted fingerprints were contacted with lifting tapes of varying adhesiveness (Tape 1 , Tape 2 and Tape 3 as above) and a portion of the latent fingerprint residue was lifted by the tapes. The residues remaining on the surface of the stainless steel target plate were re-dusted with ROAR Black magnetic powder and subsequently contacted with a lifting tape of high adhesiveness (Tape 3). The tape is then which is fixed onto a clean target plate (adhesive surface facing upwards) to ensure that the tape is uniformly flat across the plate's surface. SALDI-TOF-MS is then performed on the samples. The spectra of the second lifted prints are shown in Figure 5. The lower trace is for the first lift with Tape 3 (highest stickiness), middle trace first lift with Tape 2 (medium adhesiveness) and the upper trace is for first lift with Tape 1 (lowest adhesiveness).

Peaks of lowest intensity are seen in the lower trace where the first lift was with the most adhesive tape (Tape 3). Hence the use of tape of high adhesiveness is not recommended for the first lift as little residue is available for the second lift and hence poorer spectra are obtained.

Example 5

Fingerprints were applied to the surface of a stainless steel target plate as before. The resulting latent fingerprints were dusted with ROAR black magnetic powder as before. The latent fingerprints were contacted with tapes of varying adhesiveness (Tape 1 , 2 and 3) as before and a portion of the fingerprint residues were subsequently transferred onto the surface of the tape following removal of the tape. The remaining fingerprint residues were re-dusted using ROAR Black magnetic powder before being contacted with Tape 1 (lowest adhesiveness). The resultant second lifted fingerprint residues were then subjected to SALDI-TOF-MS. Spectra of the second lifted fingerprint residues are shown in Figure 6. The lower trace is for the first lift with Tape 1 (lowest adhesiveness), middle trace first lift with Tape 2 (medium adhesiveness) and the upper trace is for first lift with Tape 3 (highest adhesiveness)

In all three traces little detail is observed of peaks associated with fingerprint constituents compared with previous figures, indicating that the second lift with the tape of low stickiness is not lifting the residual material from the fingerprint effectively. The new peaks at 413 and 429 may be due to the adhesives in this tape (which can be transferred onto the target plates during the transfer process- see Figure 2).