Quantifying DNA loss in laboratory-created latent prints due to fingerprint processing

Area of Science:

• Forensic Science
• Molecular Biology
• Trace Evidence Analysis

Background:

• Touch DNA samples from fingerprints often yield limited DNA quantity and quality.
• Fingerprint processing techniques, including light and chemicals, can further degrade DNA.
• Current forensic practices often require choosing between DNA analysis or fingerprint analysis due to potential sample destruction.

Purpose of the Study:

• To investigate the impact of standardized latent fingerprint processing on DNA quantity and quality.
• To determine which fingerprint processing methods affect DNA recovery.
• To provide guidance on optimizing forensic analysis when both DNA and fingerprint evidence are present.

Main Methods:

• Standardized mock fingerprints were created to minimize variability.
• DNA quantitation was performed after each step of various fingerprint processing techniques.
• Fingerprint processing was conducted on both non-porous (plastic, duct tape, metal, rubber) and porous (wood, paper) surfaces.

Main Results:

• Latent print processing on non-porous surfaces did not significantly affect DNA quantity or quality.
• Ninhydrin, used on porous surfaces, significantly reduced DNA recovery.
• Other tested fingerprinting chemicals and lighting methods showed minimal impact on DNA.

Conclusions:

• DNA analysis is feasible on items processed for latent fingerprints, provided ninhydrin is not used on porous surfaces.
• The choice of fingerprint processing method is critical for preserving DNA evidence.
• Combining DNA and fingerprint data can enhance identification confidence when DNA profiles are partial.