Principles of Digital Forensics

Digital evidence is any probative information stored or transmitted in digital form. Unlike physical evidence, digital evidence is fragile (easily altered or destroyed), volatile (RAM contents vanish when power is lost), vast (a single smartphone can contain millions of files and records), and replicable (perfect bit-for-bit copies can be made). The ACPO (Association of Chief Police Officers) principles guide digital evidence handling: no action should change evidence on a device; when accessing original data is necessary, the person must be competent and able to explain their actions; an audit trail must be maintained; and the case officer bears overall responsibility. These principles parallel physical evidence chain of custody requirements but address the unique challenges of electronic data.