The invention provides an electronic security, investigation and surveillance system (10) and method involving the use of mobile electronic devices (12) such as smartphones. The system can maintain an up-to-date historical record of data and media sourced from across a broad spectrum of a mobile device's functionalities, for example its cameras, microphone, GPS system, etc. In the event a crime is committed or an emergency incident occurs in the vicinity of the mobile device, this historical record can be accessed and uploaded from the mobile device to a backend (14). The backend can also be used to assume control of the device. In common with the so-called "black box" systems found in aviation, the historical record is maintained for a limited and advancing period of time. That is, means are provided for erasing earliest data within the historical record on an advancing time basis, and/or with reference to a predetermined memory usage or storage capacity of the mobile device.