DNA deposited in whole thumbprints: A reproducibility study

Area of Science:

• Forensic Science
• Genetics
• Human Identification

Background:

• Touch DNA analysis is vital in forensics, but shedder status remains poorly understood.
• Research on DNA deposition and persistence needs more cohesive investigation.

Purpose of the Study:

• To investigate inter- and intra-individual variations in shedder status.
• To assess the impact of time post-handwashing on cellular deposition.

Main Methods:

• Ten volunteers deposited thumbprints at 15 minutes (defined) and >60 minutes (undefined) post-handwashing.
• Thumbprints on glass slides were stained with a nucleic acid binding dye.
• Fluorescent cells in 55 grid squares were counted to determine cell deposition.

Main Results:

• Shedders showed less consistent deposition in the defined condition compared to the undefined.
• Heavy shedders achieved informative profiles 73% (defined) and 87% (undefined) of the time.
• Light shedders consistently produced uninformative profiles (≤33% uploadable).

Conclusions:

• Time post-handwashing significantly impacts touch DNA yield and profile quality.
• Heavy and intermediate shedders are more likely to yield usable DNA profiles.
• Light shedders consistently yield insufficient DNA for database upload.