DNA transfer when using gloves in burglary simulations.

Area of Science:

• Forensic Science
• Genetics
• Molecular Biology

Background:

• DNA can be indirectly transferred to surfaces, meaning its presence doesn't always indicate direct contact.
• This phenomenon poses challenges in forensic investigations, particularly when a person of interest (POI) denies involvement but their DNA is found at a scene.

Purpose of the Study:

• To simulate scenarios where DNA is transferred indirectly via gloves to a surface (door handle).
• To assess the likelihood of a POI's DNA appearing on a surface when an alternative offender (AO) uses the POI's gloves.

Main Methods:

• Conducted 60 simulated burglary experiments involving DNA transfer on door handles.
• Compared DNA profiles recovered from bare-handed contact versus contact using recently worn gloves.
• Analyzed the quantity and quality of DNA profiles (NGM SElect) obtained under different transfer conditions.

Main Results:

• Less than 50% of collected traces yielded interpretable DNA profiles.
• When a POI handled a door bare-handed, their DNA was the major contributor in 30% of mixed profiles.
• When an AO used the POI's gloves, the POI's DNA was compatible with 22% of mixed profiles (major contributor in 8%).

Conclusions:

• Indirect DNA transfer, especially via items like gloves, can lead to DNA profiles that are compatible with a POI who denies presence.
• Forensic interpretation must consider alternative transfer mechanisms and the possibility of legitimate explanations for DNA presence.
• This research underscores the importance of evaluating DNA evidence within the context of specific activities and potential indirect transfer routes.