Rapid Documentation of Possible Semen Stains for Forensic DNA Profiling

Area of Science:

• Forensic Biology
• Molecular Biology
• Biochemistry

Background:

• Acid phosphatase (AP) testing is crucial for identifying semen in forensic samples.
• Current methods of marking AP-positive areas with crayon are inefficient and time-consuming.
• Streamlining forensic workflows is essential for timely case processing.

Purpose of the Study:

• To evaluate Saral Wax-Free Transfer Taper (TP) as an alternative to crayon for marking AP-positive areas.
• To assess the impact of TP pigment on downstream DNA analysis, including PCR amplification and STR profiling.
• To determine the efficiency gains of using TP for AP mapping in forensic laboratories.

Main Methods:

• Proof-of-concept study evaluating TP for tracing AP-positive areas on crime evidence.
• Real-time DNA quantification to assess PCR inhibition using internal PCR controls (IPC).
• Stress-test conditions with TP pigment inclusion to evaluate DNA yield and STR profile completeness.
• Comparative analysis of time taken for AP mapping using TP versus crayon.

Main Results:

• TP pigment did not inhibit PCR amplification, evidenced by consistent IPC C_T values.
• Complete STR profiles were obtained even under stress conditions with TP pigment.
• A five-fold reduction in documenting time for AP mapping was achieved using TP compared to crayon.
• No allele dropout was observed in STR profiles despite TP pigment presence.

Conclusions:

• Saral Wax-Free Transfer Taper (TP) is a viable and efficient alternative to crayon for marking AP-positive areas in forensic casework.
• TP does not interfere with critical downstream DNA analysis, ensuring the integrity of forensic evidence.
• The adoption of TP can significantly enhance laboratory efficiency, reducing processing times for semen identification.