Analysis of condom lubricants for forensic casework

Area of Science:

• Forensic Science
• Analytical Chemistry
• Trace Evidence Analysis

Background:

• DNA detection is challenging in sexual assault cases involving condom use.
• Condom lubricant residues are vital associative trace evidence.
• Existing Fourier transform infrared spectroscopy (FTIR) methods lack sensitivity and discrimination for lubricant analysis.

Purpose of the Study:

• To develop and validate a more sensitive alternative to FTIR for condom lubricant residue analysis.
• To establish robust analytical methods for polydimethylsiloxane (PDMS) and polyethylene glycol (PEG) lubricants.
• To assess the efficacy of new methods for detecting lubricants in forensic casework.

Main Methods:

• Analysis of condom lubricants using Pyrolysis Gas Chromatography-Mass Spectrometry (PyGC-MS) and Gas Chromatography-Mass Spectrometry (GC-MS).
• Extraction and direct analysis of polydimethylsiloxane (PDMS) and polyethylene glycol (PEG) lubricants from standard solutions, clean swabs, and postcoital swabs.
• Evaluation of method sensitivity and comparison with FTIR.

Main Results:

• PyGC-MS and GC-MS demonstrated significantly higher sensitivity than FTIR for PDMS and PEG lubricants.
• Detection limits achieved were as low as 1 µg for PDMS and 0.5 µg for PEG in standard solutions.
• Condom lubricants were successfully detected on postcoital swabs up to 12 hours after intercourse.

Conclusions:

• PyGC-MS and GC-MS are highly sensitive and effective methods for analyzing condom lubricant residues in forensic investigations.
• These methods improve upon FTIR limitations, offering better sensitivity for trace evidence detection.
• Recommendations are made for implementing these methods in routine casework with strict interpretation criteria to avoid false positives.