Postponed until further notice
Duration: 1 hour
Forensic science practitioners in both domestic and Department of Defense organizations are often called upon to build cases and attribute crimes using trace evidence remaining at a crime scene. The ultimate goal of these investigations is to associate a crime with a suspect or suspects in order to prevent further attacks through exclusion, exoneration, arrest, and criminal prosecution of potential perpetrators. However, fundamental questions remain regarding evaluation and interpretation of trace evidence for post-blast explosives attribution.
The explosive charge is an attractive component for attribution in crimes involving explosives as it is key to the functioning of the device and there are limited pathways for acquisition. However, unlike pre-blast attribution where signatures from explosive manufacturer reference samples can be compared with recovered samples, there is currently no capability to link the explosive charge to its source via post-blast trace residues. Attributing the explosive post-blast is a challenge due to environmental contamination, lower abundances of material, and potential degradation of useful signatures, which limits the analytical techniques that can be used. The purpose of this study is to determine whether pre-blast attribution signatures are preserved after detonation, and whether they can be recovered from a blast site and measured at a detectable level.
In the study, multiple field tests were conducted to recover post-blast explosive samples from controlled detonations of varied explosive materials including RDX, TNT, and ammonium nitrate-aluminum (AN-AL). Results collected during a preliminary field test have shown promise that carbon, nitrogen, and oxygen isotope ratios remain consistent pre- and post-detonation and thus could be relevant for source attribution. These results indicate that isotope ratio signatures of explosive compounds look to have been preserved after detonation in this small sample set. Samples collected from a larger field test have been analyzed and these results will be discussed in depth during the webinar. With this proof-of-concept study, the forensic community will benefit from a novel approach to attribute explosives after detonation.
3 Detailed Learning Objectives
- Attendees will gain an understanding of the post-blast sample collection and processing methods used to extract attribution signatures from multiple explosive types sample matrices.
- Attendees will obtain familiarity with the different instrumental analysis techniques used to analyze chemical attribution signatures from trace post-blast explosive residue, and which of those techniques show greater promise than others.
- Attendees will learn the data analysis approaches used to compare pre- to post-blast signatures.
Paul Ippoliti - Analytical Chemist, MIT Lincoln Labs
Funding for this Forensic Technology Center of Excellence event has been provided by the National Institute of Justice.-
Please contact us at ForensicCOE@rti.org for any questions.
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