Condom Trace Evidence: The Overlooked Traces By Robert Blackledge, MS
Writing in USA Today,1 Richard Willing states: "Prisoners and suspects across the U.S. are becoming smarter, or at least better educated, when it comes to undermining the biological evidence that often is critical in criminal cases. Police and prosecutors from New York to California report that more would-be rapists than ever are wearing gloves, masks and condoms to avoid leaving behind any bodily fluids or other evidence at crime scenes. In prison, convicts have been caught swapping semen samples to try to defeat genetic tests aimed at linking them to additional crimes. Inmates routinely share tips on how to sabotage crime scenes by, amongst other things, scattering someone else's semen or blood in order to confuse DNA analysis."
In most crime labs if no traces of the suspect's seminal fluid or other DNA sources are found, no further examinations are conducted.
Although condom use may (but not always) prevent the positive identification of a suspect through his DNA, condoms themselves have exchangeable traces that are of evidential value. Examples of exchangeable traces from condoms include lubricants, particulates and the spermicide, nonoxynol-9. Most condoms are lubricated and because they facilitate the act they are preferred by sexual assailants. By far, the most common lubricant used on condoms is a silicone oil. Because it is not water soluble, traces tend to remain in the vaginal vault for many hours and are easily recovered from deep vaginal swabs.
As her thesis project for a master's degree in forensic science from the University of North Texas, Denton, Texas, Kelly Belcher asked volunteer couples to provide vaginal swabs taken at certain time periods after sex when they had used condoms bearing this lubricant. Using an infrared spectrometer (an instrument that all crime labs have), Belcher could identify its traces even when swabs had been obtained as much as 48 to 59 hours post-coitus.2
Particulates such as corn starch, lycopodium powder, talc, fine silica and other finely-powdered minerals are added to prevent the rolled-up latex condom from sticking to itself. These too may be recovered from vaginal swabs and identified by use of a polarized light microscope (all crime labs have them), or a scanning electron microscope/energy dispersive spectroscopy system (available in most large crime labs).3
Although requiring a mass spectrometer system found only in the largest crime labs, scientists at the Scripps Research Institute in La Jolla, Calif. have reported on a method for its nonoxynol-9 recovery and identification.4
Sometimes it's a matter of "he said, she said." That is, the accused readily admits he or she had sex but says it was consensual. There are a number of commercial contraceptive products available that prior to sex must be inserted deep into the vagina, followed by a wait of about 15 minutes before being fully effective. One type consists of 2-inch by 2-inch squares of a water-soluble plastic film that is permeated with nonoxynol-9. Another product has a suppository-like appearance and has the consistency of paraffin but also contains nonoxynol-9. The finding on deep vaginal swabs of traces associated with any of these products would certainly support the suspect's claims. However, these products might also be used in order to prevent pregnancy in cases of child sexual abuse.5
One might ask, "what good would this evidence be, after all, unlike a fingerprint or DNA, it doesn't positively identify a suspect?" True, but even before DNA and even without fingerprint evidence it was possible to get a suspect convicted for sexual assault based on other evidence. Along with a colposcope exam and all the other indications documented by the forensic nurse upon examining the victim, non-biological trace evidence can assist in providing corpus delicti, that is, proof that the crime occurred. It can also show penetration. In many jurisdictions, by statute there are various levels of sexual assault. Proof of penetration can help boost the charges up to a higher level. Such associative evidence can help to connect a suspect with the crime. Let's say that the used condom was flushed and was never recovered, but its foil packet was found and on it a suspect's fingerprints were developed. The finding on vaginal swabs from the victim of condom traces consistent with that brand would support the association. The same would be true even if only unused condom packets are found in the possession of the suspect and the traces recovered from the victim's vaginal swabs match that brand.
It would appear that in the United States in general, the message is not getting through. Published in , Drug-Facilitated Sexual Assault -- A Forensic Handbook, edited by Marc A. LeBeau and Ashraf Mozayani, Academic Press, consists of 13 chapters written by various contributors. The use of a date rape drug such as GHB or Rohypnol, combined with condom use makes these cases especially difficult to prosecute. Yet in only one chapter is condom use mentioned, and even in those few paragraphs it is assumed that the used condom was recovered at the crime scene (it rarely happens). In chapter 11, of "Sexual Assault Nurse Examiners," written by Linda Ledray, RN, PhD, FAAN, director of Sexual Assault Resource Service in Minneapolis, there is no mention of condom trace evidence even though there is a separate section on "additional sources of evidence." No mention either in chapter 12, "Investigating DFSA Cases" or in chapter 13, "Prosecution of DFSA."
However, there are a few encouraging signs. While a graduate student working on his master's degree in forensic science from the John Jay College of Criminal Justice of the City University of New York City, Stewart Hung worked as an intern in the New York City Medical Examiners Office (MEO). As his thesis project, he used infrared spectroscopy to examine vaginal swabs from those sexual assault kits that had proved negative for seminal fluid. The silicone oil condom lubricant was identified in approximately 7 percent of more than 400 cases.6 Based on these findings, the New York City MEO is now introducing a routine protocol of checking for this lubricant in those cases that are negative for seminal fluid or where the victim claims the suspect wore a condom. Similar protocols are currently in use at the New Hampshire State Police crime lab and at the U.S. Army Criminal Investigation Laboratory (USACIL).
A catch-22 exists. As forensic nurses, you are well aware that some individuals are deathly allergic to latex products. For these susceptible individuals, even casual contact with latex can cause their body to go into life-threatening anaphylactic shock. This reaction is triggered when the body's immune system identifies as foreign invaders the soluble plant proteins present in latex. Since upon exposure to latex these soluble plant proteins will be present whether or not one has a latex allergy, a positive test for these proteins would indicate exposure. Enzyme linked immunosorbent assay (ELISA) is a highly sensitive and specific test. In December scientists from The Scripps Research Institute submitted a grant proposal to the National Institute of Justice (NIJ).7 It is doubtful that any research organization in the world has more experience and expertise than Scripps in the area of antibody/antigen chemistry. The ultimate product of this research would have been to produce a simple kit that at a cost of one or two dollars per test would in a few minutes indicate whether residues present on a cotton swab were consistent with exposure to latex. Much of the basic research had already been done, but with latex gloves rather than condoms. The research with gloves indicated the latex-soluble protein profile was altered by the glove-manufacturing process. Because of this, it was anticipated that differences in profiles might be seen between different condom manufacturers. The grant proposal was turned down by the NIJ. The committee that reviewed the proposal was not convinced condom use by sexual assailants was a serious problem.
Although sexual assault victims are routinely asked about condom use when interviewed by forensic nurses, and although the FBI keeps annual statistics on sexual assaults, no nationwide statistics are kept on the frequency of condom use in these assaults. However, Terry Cook, a criminalist with the Las Vegas Metropolitan Police Department crime laboratory, researched records of sexual-assault kit submissions from Sept. 10 to Dec. 3, . In roughly 1 in 4 cases the victims' statements indicated use of a condom by one or more assailants.8 Additionally, for his thesis project for a master's degree in forensic science from National University, Calif., Christian Bourdages in examined the paperwork filled out for sexual assault victims in San Diego County in the years , , and up to Sept. 30, . For that period he found that out of a total of 439 cases, in 54 cases condoms were known to have been used during the assaults (12 percent).9
Condom traces may provide valuable associative evidence in sexual assault cases and cases of child sexual abuse, but until sexual assault investigators and forensic nurses learn to look for and collect these traces and then demand that crime laboratories conduct condom trace evidence examinations and comparisons, this evidence will remain the overlooked traces.
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Robert Blackledge, MS, is the senior chemist at the Naval Criminal Investigative Service Regional Forensic Laboratory in San Diego. |
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