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In an age filled with potentially fatal sexually transmitted diseases, more and more individuals practice safe sex. Even perpetrators of sex crimes have begun to wear condoms.1 It is not likely that a fear of disease prompts this behavior. Rather, just as a burglar dons gloves to avoid leaving fingerprints, sexual offenders now wear condoms to avoid depositing seminal fluids.
Forensic experts typically identify sexual assault offenders by examining seminal fluid residues for sperm, proteins, blood grouping factors, and DNA profile. When sexual assailants use condoms, however, assuming no leaks or spills, this valuable evidence gets trapped inside the condom, which investigators may never recover. The same can be said for any traces from the victim-including vaginal cells, blood, and saliva-that otherwise might have been transferred to the assailant's penis. Nevertheless, when assailants use condoms, they leave behind other valuable evidence.
TYPES OF CONDOM TRACE EVIDENCE
Manufacturers produce condoms using a variety of materials, both natural and synthetic. Each manufacturer has its own formula, which may vary even among its different brands.
Some condoms are made from lamb membranes, and one manufacturer recently introduced a model made from polyurethane plastic. Still, latex rubber condoms have, by far, the largest share of the market, perhaps because they cost considerably less. In addition to the basic materials they use to produce condoms, manufacturers also add other substances, known as exchangeable traces, which comprise particulates, lubricants, and spermicide.
Particulates
Condom manufacturers add finely powdered particulates to prevent a rolled-up latex condom from sticking to itself. Particulates found in different brands include corn starch, potato starch, lycopodium (a powder found in plants), as well as amorphous silica, talc, or other minerals. In the laboratory, forensic scientists use several different techniques to characterize these particles and compare them with those obtained from other condom brands.
Lubricants
Sexual assailants prefer lubricated condoms, probably for the same reason that they use petroleum jelly, that is, to facilitate their crimes.2 Many condom brands contain a liquid lubricant, which may be classified as either "wet" or "dry."
Both types of condom lubricant have an oil-like consistency, but wet lubricants are water-based and/or water-soluble, while dry lubricants are not. Although many different manufacturers use the same dry lubricant, their viscosity grades sometimes differ. The forensic...