Instrumentation & Measurement Magazine 24-1 - 26

starts to exhibit a symptom that is typical of thallium poisoning: a dark pigmentation will begin to appear around the roots
of the hair. This symptom rapidly progresses to complete loss
of the hair and alopecia. For this reason, the United States
Central Intelligence Agency, in addition to several hundred
unsuccessful attempts to assassinate Fidel Castro, tried to organize a Character assassination using thallium salts spread on
the shoes, to destroy Castro's famous beard [8].
There is no real antidote for thallium poisoning, in the sense
that there is no known agent that will remove thallium from
the body once it has already been absorbed in the gastrointestinal tract. However, a number of agents can be administered
to prevent it from being absorbed or reabsorbed. The primary
agent used in cases of poisonings is Prussian blue, although
it is toxic itself and must be administered in moderate doses.

Arson
Arson is a serious crime that affects society through cost, property damage, and loss of life. Everybody nowadays has heard
of the terrible arsons that occurred in several part of the world
and in particular in the last few years that involved the Amazonian forest and the Australian continent. A well-studied case,
which brought to arrest the arsonist is reported, although it is
not as impressive as those presented before.
Throughout the 1980s and 1990s, California was plagued
by a series of arson fires: one of the fires resulted in the loss of
65 houses, and another fire in an hardware store killed four
people. Investigators combed the areas and searched for clues;
however no clear pattern was found. An investigator noticed
the odd coincidence that the pattern of arsons was occurring
near the city of Fresno that was the host city of a convention of
arson investigators. The police started with a list of 55 possible
suspects that after several years and fires was finally narrowed
down to John Orr, a respected arson investigator, who was
convicted of four murders and sentenced to life plus 20 years
in prison without the possibility of parole. Arson investigators and criminal profilers defined Orr the Pillow Pyro, one of
the worst serial arsonists of the 20th century. Orr used the same
incendiary device for all of his nearly 2000 blazes: a cigarette
attached to a book of matches wrapped in paper with cotton
and bedding, hence the nickname, secured with a rubber band;
the cigarette would burn down, and the matches would ignite
the paper and bedding.
The methods and technologies applied by fire investigators in detection of evidence and subsequent analyses had
considerable advances since 1950, increasing their degree of
reliability and sensitivity, and were more and more subject
to rigorous quality control and assurance. The classification
of ignitable liquids is continuously updated to include many
new categories due to developments in the petroleum industry. Techniques such as steam or vacuum distillation and gas
chromatography (GC) with flame ionization detection considered acceptable, even a benchmark, forty years ago, are
nowadays generally disfavored, to the extent that their implementation may almost be considered as ignorance in the field.
The advent of readily available mass spectrometric techniques
26

has revolutionized the field of fire debris analysis, noteworthy increasing the degree of sensitivity and discrimination [9].
Multi-dimensional GC, particularly GC x GC, Comprehensive
Two-dimensional gas chromatography, while not yet widely
applied, is rapidly gaining recognition as an important technique [10].
In the field of investigation of arson fires there is a continuous research of more efficient and sensitive vapor collection
methods as this one that involves the dynamic adsorption of
headspace vapors on short porous layer open tubular (PLOT)
columns maintained at low temperature, around -40 °C. The
collection sensitivity is high, below 1 part per billion (ppb). The
low temperature is achieved using a vortex tube connected to
compressed air, with no moving parts, good for use in environments with explosive or flammable materials. After vapor
collection, the PLOT capillaries can be heated, up to 160 °C,
releasing the vapor. The PLOT-cryo method can be used to simultaneously test for up to eight different ignitable liquids
from a single sample, allowing investigators to take multiple samples from each of several locations in a fire scene in a
short time.

Fires, Explosions
In may be interesting to underline that the Forensic Chemistry
approach is important in assessing liability for events such as
fires that are not always intentional arsons, as described before,
or explosions. As a matter of fact, the use of explosives may
be legitimate, as in mining activities and military operations,
or may be illegal, to cause death and destruction by criminals
and terrorists. Consequently, the main goal of an investigation
on explosives is to assess if the event is accidental or deliberately set up. Several analytical techniques are used to analyze
the post-blast explosive residues; the most popular are infrared
spectroscopy, Raman spectroscopy, gas chromatography/mass
spectrometry, and energy dispersive X-ray analysis.
An accurate investigation of the blast site is of outstanding importance, from structural damages to injuries, to the
collection of fragments, such as circuit boards, switches, or
timers possibly coming from the exploded device, accelerants, tampered utilities, specific burn patterns in case of fires,
and residues of the explosive. To identify the chemical composition of the explosive, Forensic Chemists may utilize in
situ analytical techniques, such as ion-mobility spectrometry
(IMS), commonly used to separate and identify ionized molecules in the gas phase on the basis of their mobility in a carrier
buffer gas. In particular, hand-held IMS detection devices are
used to characterize residues present around the blast site [11].
Dealing with fires, in addition to ultraviolet, infrared and
nuclear magnetic resonance spectroscopy to identify accelerant components, the most widely used technique is gas liquid
chromatography, which is able to separate and detect trace
amounts of volatile hydrocarbons in complex mixtures, such
as the four most common accelerants petrol, kerosene, mineral
turpentine and diesel. Even if the samples are evaporated and
contaminated, Forensic Chemists are confident in identifying these compounds on the basis of their gas chromatograms.

IEEE Instrumentation & Measurement Magazine

February 2021

Instrumentation & Measurement Magazine 24-1

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