What Criminal Lawyers Should Know — and Why IT is dangerous

What lawyers are told “touch DNA” means

• skin cells shed through casual contact
• objects handled briefly
• surfaces exposed to indirect contact

Why the term is scientifically outdated

• direct contact
• secondary transfer (via another person or object)
• Indirect transfer (meaning more than one intermediary transfer step)
• environmental movement
• background DNA accumulation

The risk in criminal cases

• the DNA must result from direct interaction
• the interaction occurred during the alleged incident
• alternative explanations are unlikely

• DNA can transfer without direct contact
• low-level DNA may persist over time
• background DNA may be present before an alleged event

Why this is difficult to explain without expert evidence

• DNA presence does not equal proof of contact
• secondary DNA transfer (indirect transfer) is scientifically plausible
• low-level DNA findings should be interpreted cautiously

The role of independent expert review

• explaining scientifically recognised transfer mechanisms
• identifying whether alternative pathways remain plausible
• clarifying the limits of inference
• providing a balanced framework for evaluating probative value

A broader issue DNA transfer in criminal casework

Final observation