The Particle Articles

Recently, Gateway Analytical scientists Cara Plese and Antonio Scatena presented a half hour webinar focused on the forensic analysis of condom lubricants. The webinar covered the collection, documentation, and investigative value of condom lubricants and sexual assault evidence along with discussing the scientific principles and current methods of condom lubricant analysis.

The webinar was well received, and the attendees had some great questions. You can find the transcribed Q&A, and a copy of the presentation below. For any additional question on the webinar or relating to condom lubricant analysis please contact us directly.

Download: Forensic Analysis of Condom Lubricants for Police & Attorneys
Replay Webinar: Forensic Analysis of Condom Lubricants for Police & Attorneys

1. Can you talk about timeframe for finding lubricants?
   The dry lubricants (PDMS based) will remain until washed away.  Things such as showering, going to the bathroom, and menstruation can cause the PDMS and starch particles to be washed from the system, and therefore they may not be collected.  Even if time has gone by between the incident and the collection, or if the victim admits to showering, it is better to collect evidence regardless, as traces may still be present.  Even if the results are negative, it can be explained that the lubricant traces may be absent due to the length of time between incident and collection.
2. As a SANE nurse, how do I collect the evidence? I believe we need separate swabs and do we need to include a glove sample?
   As a SANE nurse who would be collecting the evidence, it is important that, if possible, you do not use powdered gloves, as these may contain starch or talc particles which could contaminate the samples.  If it is unavoidable, and powdered gloves must be used, it is a good idea to submit a glove for testing as a control so that if it doesn’t contain any particles of interest it can be eliminated as a source.  If multiple swabs are collected from different areas on one victim, it would be advantageous to separate them.  For example, if one swab was collected from the inner thigh area, and one from the inside of the vaginal vault, and these were packaged together, a positive result from the vaginal swab could be due to contact with the inner thigh swab.  The difference is that a positive result from vaginal swab would be evidence of penetration and the swab from the inner thigh would be evidence of contact.
3. Have you considered saliva samples for oral sex rape cases?
   We have not, as of now, performed this type of analysis.  These samples could be collected, however I believe that the timing after the incident would be crucial in this case as the nature of swallowing and salivation would cause the traces to be lost quite quickly.  Additionally, starch is present in lots of foods, so its presence in the mouth would not be as meaningful as it would be in other orifices.
4. What is your experience in casework with timeframe?
   The timeframe required for analysis of a condom lubricant case would be dependent on the number of samples/swabs submitted.  The majority of the time devoted would be to preparation of the samples.  Usually, a condom lubricant case can be completed within a day.
5. Can you visualize the starches or other components of condom lubricant using only light microscopy, as opposed to polarized light microscopy? If so, what do the component(s) look like?
   It is important to use PLM to view particulate in condom lubricants.  The reason being that the maltese cross observed on starch particles when viewed between crossed polars is unique to starches.  When viewed with light microscopy, these particles would appear as circular, an appearance which is shared with many other types of particles and therefore is not specific.
6. Do you analyze for the presence of PDMS using GC/MS?
   We do not use GC/MS in our laboratory, however it can be used to analyze for the presence of PDMS as well as other components such as nonoxynol-9.
7. How many vaginal swabs do you need?  Is it ok to swab a discarded package (as a known) to send to you so we can keep for fingerprinting?
   Just one swab can be submitted for analysis.  If there are swabs from different areas, it may be advantageous to submit one from each representative area of sampling.  Yes, you can swab the inside of a wrapper and submit that as a known lubricant sample and retain the wrapper itself for fingerprinting analysis.
8. Would your analysis allow for comparison of vaginal vault swabs from victim with an opened and empty condom wrapper - same type of lubricants present?
   If there is lubricant present on the interior of the wrapper, it would be possible for a comparison to be made to lubricant recovered from a victim swab sample.  Things that could be compared would be presence or absence of spermicide (nonoxynol-9), presence of wet vs. dry lubricant, presence of particulate (potato starch, corn starch, lycopodium), etc.  It is important to note however, that a comparison could indicate an association with a brand of condoms, however we cannot identify a source as a specific condom.  A comparison is a good way however, to eliminate brands of condoms.