Forensic Department "Environment-Fire-Explosives"
Forensic Expert - Forensic Department "Environment-Fire-Explosives", IRCGN
In a sexual assault situation, biological traces usually constitute the most valuable evidence for the identification of the offender. Unfortunately over the past decade, the use of condom increased significantly in rape cases in order to avoid leaving DNA on the crime scene. Therefore the detection of condom lubricant will become essential when biological evidence is lacking. Lubricant or another slippery substance could also be employed to facilitate the sexual assault.
Chemical analysis of vaginal or anal samples can provide investigators leads and insights on to the perpetrator of a rape.
The composition of lubricant products is mainly silicone-based (PDMS), polyethylene glycol (PEG)-based, water-based (with glycerine) or oil-based (petroleum grease). Formulations often contain additional compounds as spermicide, aroma
and anesthetic. The overall challenge is to successfully identify the whole composition of lubricant which nearly requires as many techniques of analysis as types of compounds. It would be interesting to be able to discriminate between lubricant products and condom brands. To avoid false positives, a focus must be made on the specificity of compounds since many of them could be found in other commercial products.
Based on previous published forensic works, research was done to establish an efficient strategy of analysis to highlight compounds from lubricant products. The preparation of samples and choice of analysis techniques (FT-IR, LC-HRMS, Py-GC-MS and GC-MS) will be discussed and characteristic profile patterns of formulation shown.
Twenty different types of commercially available condoms and personal lubricants were analyzed in order to have an overview on the composition of the French market lubricant products.
Studies of the persistence of lubricants and effects of biological fluids have also been undertaken with volunteers’ vaginal swabs.
Condom, Lubricant, Sexual Assault