On August 8th, David Exline, Senior V.P. & Court-Qualified Trace Evidence Expert and Rebekah Wagurak, Forensic Scientist at Gateway Analytical presented a webinar that covers the forensic investigation process for paint and tape evidence. Topics include the most current methods used for today’s investigators and discuss the interpretation of paint transfer evidence. Case studies related to the analysis of duct tapes, automotive and architectural paints were also discussed.
During the webinar, attendees participated in a Q&A session. You can find the transcribed discussion below along with other resource links for this webinar.
- Can one determine the brand of tape through analysis?If you examine the physical and chemical characteristics of tape such as color, size and composition of backing ; composition of adhesive, thread count, as well as trace components in adhesive, you can obtain a general classification/potential brand of duct tape being used.
- How long does an analysis of either of type of evidence typically take?Typically: tape single sample about 4 hours. Same with one sample of paint for a single sample. Cases typically involve at least 2 samples (known and questioned).
- How large of a sample would you need to perform an analysis?For tapes and paints one doesn’t need a large sample, but do need a complete sample, with the most probative being those will complete layer systems. For example, if you have a fragment of tape/paint a paint analysis can be performed, however, the degree of informantion and possible association is not as strong as if you had a complete sample for fracture matching or that contained all of the various layers.
- Is there any direct correlation between how long a piece of duct tape has been applied to a surface and how much of the adhesive sticks when removed to help in any analysis or are the factors (i.e. various manufacturers, brands, environment, surface, etc.) too diverse for this sort of comparison?The recipient garment will have a lot to do with the adhering of duct tape and the shedabliilty. A lot of factors go into the degree of adhesiveness/removability of the tape, and depends on previous environment of the tape and heavily on the recipient surface of the tape.
- Do the different colors of duct tape tend create problems in duct tape analysis?The colors add value as color is often the more discrimination/variability between brands/within brands adds degree of association. If we have different shades of same color duct type, slight shade differences between different lots of the same color may increase discrimination.Many designer styles/colors of Duck brand now exist and add to the discrimination/variability of duct tapes.
- From a forensic perspective that is an advantage.From your experience have you had any success in obtaining DNA from the adhesive of duct tape, and if so how? - for example in cases where duct tape is used as a gag or to bind hands?Yes there has been success in extracting DNA from tape samples.