Screening Physical Evidence at the Crime Scene

Through the National Criminal Justice Reference Service, NIJ has made available a final technical report that discusses the application of a "broadly applicable, portable chemical detector based on a state-of-the-art mass spectrometer (MS) capable of sampling externally generated ions."


Accessing the Probative Value of Physical Evidence at Crime Scenes with Ambient Mass Spectrometry and Portable Instrumentation

Christopher C. Mulligan, Ph.D., and Adam E. O’Leary


The amount and variety of evidence collected at a typical crime scene is extensive. While many significant analytical methods have been established over the years, particularly hyphenated mass spectrometric techniques, forensic laboratories cannot keep up with the demand, and in many cases, significant backlogs of evidence have amassed. While this points to a need for more rapid, streamlined technologies for forensic analysis, a significant reduction in collected evidence, leading to a subsequent reduction in backlogged evidence, would come from the ability to access the probative value of chemical evidence at the crime scene itself—allowing only pertinent samples to be sent to off-site laboratories for confirmation.

Screening of physical evidence at the crime scene also has the capability to rapidly determine whether a criminal investigation is needed and provide law enforcement personnel with necessary information in a timely manner, which in many cases is crucial. To assist in the reduction of collected samples while increasing the overall quality of said evidence, it would be beneficial for forensic science practitioners to have technology at their disposal that is not only portable—allowing the screening of potential evidence before collection—but also flexible in terms of chemical species and sample substrates that can be analyzed.

In an effort to fulfill the current technological needs of forensic science practitioners and associated laboratories, the authors sought to create a broadly-applicable, portable chemical detector based on a state-of-the-art mass spectrometer (MS) capable of sampling externally-generated ions. This capability allows the use of novel “ambient” ionization methods that allow direct screening of target compounds or “analytes” in their native environment and state without prior preparation.

The Flir Systems AI-MS 1.2 was demonstrated to be a broadly-applicable, portable instrument with high potential for use in crime scene investigation and evidentiary analysis. The flexibility to screen and identify solid, liquid and gas-phase analyte when utilizing the suite of ionization methods developed and/or investigated on the system has the potential to provide capabilities that no other fieldable technology currently available can offer. The only class of forensic evidence where the Flir AI-MS 1.2 failed to meet expectations was military grade explosives.

Click here to read the full paper (pdf, 141 pages).

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