When the Evidence Changes After Collection
DNA Does Not Stay Where It Was Deposited
- – transfer from the original deposit site to other areas of the same item
- – transfer onto the inside of the packaging
- – transfer between multiple items packaged together
Why This Matters in Criminal Cases
- – on areas of an item that were never directly contacted
- – on secondary items packaged together
- – in locations later relied upon to infer how an offence occurred
The Problem Is Not Just Transfer – It’s Interpretation
- – the activity-level meaning of the result may be overstated
- – apparent “contact” may never have occurred
- – the probative value of the evidence may be materially weaker than the statistic suggests
Common Casework Scenarios at Risk
- – clothing items packaged together
- – cigarette butts stored in a single envelope
- – gloves or tools co-packaged in bags
- – swabs losing DNA to their containers before testing
Why These Issues Are Often Missed
- – how tightly an item was packaged
- – whether multiple exhibits shared packaging
- – whether internal packaging surfaces were examined
This Is Where Expert Review Becomes Critical
- – understanding DNA transfer and persistence science
- – careful review of collection and packaging records
- – activity-level evaluation, not just source attribution
- – awareness of how courts assess probative value and unfair prejudice