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event, to have insights on the identity of potential suspects,
became more and more evident [18]. Consequently, real-time
and on-site forensic investigations gained increasing popularity because they avoid the delays that occur when evidence has
to be collected, delivered and analyzed in laboratory. On-site
devices have revealed their usefulness in the investigations on
sexual aggressions: a simple preliminary on-site DNA analysis could help to decrease the number of suspects, to focus the
work of police authorities.
Recently, the number of presumptive tests for screening
samples is noticeably increased due to the development of portable sensors, chip-based systems and handheld instruments
for in-field analysis of forensic interest, as well as of robust
and validated methods capable of providing reliable analyses
on the crime scene. Miniaturized platforms including electrochemical sensors, paper-based analytical devices, microfluidic
devices and portable instruments like mass, Raman and nearinfrared (NIR) spectrometers allow this improvement in
reliability of measurements, in the lower consumption of sample and reagents, in the low-cost per analysis and in the need
for minimal instrumental training.
Electrochemical methods satisfy most of the above-mentioned requirements for on-site and in-situ measurements,
and furthermore, the use of sensor strips, e.g., screen-printed
electrodes (SPE) instead of the conventional three-electrode
electrochemical cells, overcame the difficulty in electrodes
handling and the need for frequent calibration due to poor stability as a function of time due to electrode poisoning.
From one side, the detection of potentially explosive compounds and drugs will take advantage of different possible
approaches, from paper-based devices to the electrochemical
and microchips electrophoresis methods of similar sensitivity. From the other side, the constant development of portable
mass spectrometers and NIR analyzers provides a powerful way to identify new substances. In any case, the portable
instruments offer great advantages for forensic applications
including rapid, sensitive and accurate analysis of abused
drugs, banknotes, questioned documents, and signatures as
well as the real possibility to use them at airports, seaports
and police operations at borders between neighboring countries. Finally, the coupling of wireless data systems for data
acquisition and transmission and simpler readout interfaces
for operators to reduce subjectivity and allow rapid decision
making will further increase the versatility of portable devices.

Forensic Chemists, for example in the field of toxicology,
carry out both quantitative and qualitative analytical measurements, but do not consider or provide the formalization
of measurement uncertainty, although they have a conceptual understanding of measurement uncertainty. To actually
compute a statistically valid estimate of uncertainty, taking
into account all the relevant factors, is not easy, and Forensic
Chemists prefer to report it in an intuitive form that is intelligible for a jury. As a matter of fact, the primary customers of
forensic chemical analyses are the courts and members of the
legal community, who previously were not too convinced of
the relevance of measurement uncertainty. Nowadays, in several jurisdictions the legal community is becoming more and
more aware of the concept and is now demanding uncertainty
evaluation, in order to judge the quality and validity of the
presented measurements. This renewed interest in measurement uncertainty is favored by reports such as the 2009 one of
the National Academy of Sciences, that highly criticize the lack
of a strong scientific foundation for the claims and practices of
Forensic Sciences [20].
The study of uncertainties that arise in measurements and
propagate through calculations and inferences are of noteworthy importance for arriving to reliable conclusions in DNA
sequencing applications. The dramatic increase in the measurements made at the biochemical and molecular level has
to be attributed to development of high-throughput DNA
sequencing technologies. As a matter of fact, the different
DNA-sequencing technologies produce data with their own
platform-specific errors and biases which have a wide range of
variation. Several statistical studies were performed with the
aim of measuring error rates for basic determinations; however, no general scheme is sufficiently able to project these
uncertainties to assess the reliability of the conclusions drawn
about biological, genetic and epigenetic questions. Both uncertainty in the quantification in DNA sequencing applications
and descriptions of the sources of error need to be deepened,
as well as the proposal of methods that can be used for accounting and propagating these errors and their uncertainties
through subsequent calculations [21].
As a final observation, in Forensic Chemistry and more
generally in Forensic Sciences, there is, without any doubt, a
need to address more widely the issue of measurement uncertainty and to develop competencies in computing, reporting
and explaining this fundamental item.

Measurement Uncertainty in Forensic
Chemistry

Concluding Remarks

Only in recent times in Forensic Chemistry and Toxicology has
more attention been paid to measurement uncertainty of critical quantitative values, such as mass, concentration, purity, or
volume, thus introducing a new level of anxiety among many
forensic scientists. This reaction occurs with other unfamiliar concepts, notwithstanding the fact that ISO 17025-based
accreditation programs have the essential requirement of uncertainty evaluation of a critical measurement for analytical
laboratories seeking and maintaining accreditation [19].
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To conclude this brief introductory work, it is interesting to
note that Forensic Chemistry is becoming more and more
popular as shown by the diffusion all over the world of
prime-time television programs such as CSI: Crime Scene Investigation, Law & Order, Criminal Minds, and Cold Case
which all center on the criminal justice system. The vision
that is conveyed in these programs, of being able to solve
crimes through very complex investigations in one hour or
less, is very optimistic although stimulating for the viewer.
Unluckily, in real life the collection and analysis of evidence

IEEE Instrumentation & Measurement Magazine	

February 2021
Instrumentation & Measurement Magazine 24-1

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