Page 255 - Advances in Forensic Applications of Mass Spectrometry - Jehuda Yinon

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ignitable liquid. Thus, GC/MS/MS has shown that some GC/MS results can
be falsely reported as negative.
In general, scientists must gravitate towards more specific methods that
provide more confident results that will represent the true contents of forensic
samples. There is a concern among forensic scientists that any improvement
in sensitivity will result in positive results for nearly all samples and will weigh
heavily on the legal process, thus automatically invoking the word “arson.”
Due to the specificity of GC/MS/MS the apprehension of finding an ignitable
liquid in virtually every sample due to an increase in sensitivity is unfounded.
In court, the forensic scientist can only attest to the contents of the
sample, analyzed to his/her best capabilities. However, the forensic scientist
should also be responsible for helping investigators, lawyers, and the court
by making them aware of potential incidental sources, and thus helping
ensure that the data is reviewed appropriately in litigation proceedings. As a
minimum, ASTM recommends that a report should state in a footnote the
meaning of negative results such as “A negative result does not preclude the
possibility that an ignitable liquid is present in the sample at a concentration
lower than the method can detect, or that an ignitable liquid may have been
present in the sample at some point in time.” Perhaps forensic scientists
should also be incorporating a statement on positive results such as “Positive
results should also be reviewed in terms of the sampling location and history
to ensure that any incidental material or external sources that may be respon-
sible for the positive result are reviewed and assessed.”
Some comments regarding a new, more sensitive technique revolve
around the danger of identifying an ignitable liquid that may be present due
to environmental conditions or some previous incidental material. This con-
cern has been addressed. 15,22–24 Of course, the positive identification of a
sample with a minute quantity of gasoline from an area of a garage must be
carefully reviewed by the investigator vs. the presence of the same substance
in a sample of pillow foam from a couch in the living room, if we use a house
for an example. The forensic scientist is responsible for interpreting the
sample and not the circumstances. However, it would be prudent to make a
statement to ensure that the investigator will review information regarding
the location and history of the sample.
GC/MS/MS is a proven technique and has previously been presented in
court. Specifically, the analysis of fire debris samples by GC/MS and
GC/MS/MS has been used in a case and was described in a testimony of a
first-degree murder trial in January of 2002 in Ontario, Canada.
The advantages of GC/MS/MS significantly outweigh any disadvantages,
and it is a most valuable tool for helping the forensic scientist interpret
complex samples such as ignitable liquids in arson cases.

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