It is not uncommon for an individual to commit arson as a method of concealing a crime, whether the goal be to destroy a body, DNA evidence, or any other information that may link the suspect to the scene. Fortunately, for investigators, setting a fire to the crime scene does not always destroy all evidence. Some pieces of evidence are more resilient than others. For example, evidence such as ignitable liquids and other accelerants can often be detected after the fire. In the event that an item of evidence like clothing is not completely incinerated, the presence of biological fluids may also be detected through presumptive testing and eventually lead to the identification of an individual through DNA analysis.
The purpose of this study was to determine whether or not DNA analysis can be performed effectively after heated passive headspace concentration, without causing irreparable degradation to DNA evidence. Heated passive headspace concentration is a common procedure for extracting ignitable liquids from a substrate to identify and confirm the presence of that substance. This process requires long incubations at fairly high temperatures within a tightly sealed vessel to prevent evaporation. If practitioners can delay DNA analysis steps, move straight into heated passive headspace concentration, and lower the chances of losing a portion of the ignitable liquid to evaporation, it may assist in arson investigations. This study explores DNA quantity and quality in saliva and semen stains after incubation times and temperatures based on the recommended upper and lower temperature and timeframe limits of ASTM Guidelines E1412-19 and E1388-17 entitled “Standard Practice for Separation of Ignitable Liquid Residues from Fire Debris Samples by Passive Headspace Concentration with Activated Charcoal” and “Standard Practice for Static Headspace Sampling of Vapors from Fire Debris Samples,” respectively. Possible DNA analysis inhibitors such as gasoline, open flame, and burnt substrate were also explored. It was determined that while open flame in direct contact with a biological stain caused significant damage in all saliva stains and some semen stains, the presence of gasoline and burnt substrate did not appear to inhibit DNA analysis. Additionally, heated passive headspace concentration conditions did not appear to cause significant degradation or inhibition that would result in an incomplete genetic profile. Further experimentation is necessary given the presence of extraneous factors. For example, the initial amount of DNA deposited onto substrates was unknown. However, it is reasonable to state that performing heated passive headspace concentration before DNA analysis may be a feasible option if desired in a forensic laboratory.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/43864 |
| Date | 10 February 2022 |
| Creators | McGann, Cassidy |
| Contributors | Hall, Adam B. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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