Investigation

Physical evidence

The three physical evidence strategies are built on the foundation of Locard’s Principle of Exchange, which states that ‘every contact leaves a trace’. They are:

  • crime scene strategy (see managing scenes)
  • forensic strategy
  • pathology strategy.

These three strategies are intricately interwoven and investigating officers should keep the objectives and outcomes of all three areas in mind when developing, reviewing and managing these strategies.

Types of physical evidence

  • physical material, eg, what has the offender touched and how was entry gained?
  • victim incapacitation, eg, what weapons were used?
  • sexual evidence
  • forensic awareness, eg, did the offender wear gloves?
  • offender injuries, eg, was the offender injured?
  • missing items, eg, what was stolen?
  • blood distribution, eg, which escape route was taken?
  • linking evidence, eg, what evidence would link the offender to the scene?

Forensic strategy

The forensic strategy enables the potential of material recovered during crime scene examination to be maximised, and can help with:

Table describing ways in which a forensic strategy can help.

Forensic samples may provide information for use during interview to test the reliability of an account. They may also assist in prioritising lines of enquiry or submitting particular items for examination.

The investigating officer should also consider both examination of results and exhibits management.

Assistance can be obtained from:

  • crime scene investigators (CSIs)
  • crime scene managers (CSMs)
  • force forensic advisers
  • forensic search advisory group via the NCA Specialist Operations Centre.

For serious or complex investigations, more information on setting a forensic strategy can be found in managing major investigations (forthcoming).

Examining results

The investigating officer should carefully examine forensic results to determine their meaning. To confirm or help with interpretation, the investigating officer should seek advice and clarification from a CSM, forensic liaison or the forensic provider.

Exhibits

An exhibits officer is required in serious or complex investigations, as the number of items or exhibits may be substantial.

Page last accessed 11 December 2018