Overviewe of trace evidence

Transfer

The movement of a material between one or more sources.

Transfer considerations

• Relevance to the case

• Probative value- how relevant the evidence in proving fact in a legal case.

• Two way transfer

• Is this primary, secondary or tertiary transfer/ non contact transfer

• Absence of evidence does not mean it was never there

Considerations after transfer

• Nature of trace as some transfer and shed e.g wool easier than others

• Nature of contact

• Frequency

• Surface area

• Time frame

Persistence

 The dictionary describes persistence as “the continued or prolonged existence of something”. this leads to other questions such as; is the transfer permanent, what happens if there were multiple transfers, what happens to the trace once the transfer has occurred?

Persistence considerations

• emergency service intervention

• Contamination

• Post- deposition activity

• Environment i.e organisms

• •Crime → recovery time

  •Recovery → analysis time

What can effect detection, collection and analysis of trace evidence?

• Scene tampering inc emergency services

• Trace is not detected or detected and not recognised

• Not relevant to case

• Overwhelming amount of trace

• Inappropriate storage/ collection / interpretation

• Destructive analytical technique

Recovery considerations

• Trace or entire item

• Gloved hand or tweezers

• Wet sample?

• Sequential vs zonal tape lifting

• Vacuum sweeping non

• Swabbing

• Controls

• ELSA (not only for footmarks)