Portable NIR Spectrometers Enhance Flexibility in Forensic Science

A few months ago, the editors of Spectroscopy launched the “The Future of Forensic Analysis,” spotlighting the ongoing research in forensic analysis, and how spectroscopic instrumentation is contributing to the growth of this field (1). One of the current ongoing trends in the field that we learned as we spoke to subject matter experts (SMEs) in the field was the continued push for portable instrumentation (2–4).

Two forensic investigators in protective gear examine a crime scene in a dense forest, marking evidence near a body covered with a white sheet, surrounded by lush greenery. Generated with AI. | Image Credit: © Milos - stock.adobe.com

A recent review article published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy explored this trend in forensic analysis (5). Led by lead author Celio Pasquino from Universidade Estadual de Campinas (UNICAMP), he and his research team explored how miniaturized near-infrared (NIR) spectrometers are being used in forensic science, showing that these compact, portable instruments are redefining field-based analysis by providing reliable, cost-effective, and accessible tools for law enforcement and forensic professionals (5).

Forensic science plays a critical role in criminal investigations, offering objective evidence for cases ranging from illicit drug trafficking to food fraud (1–5). Among the arsenal of analytical tools available, vibrational spectroscopy, particularly in the NIR range, has emerged as a key player. Its ability to analyze samples quickly, often without destroying evidence or requiring chemical reagents, makes it indispensable for forensic applications (5).

Compact NIR spectrometers have helped make forensic analysis easier. Some of the benefits of using portable NIR spectrometers include the flexibility to pair them with cell phones, tablets, or laptops for data processing (5). These instruments are significantly more affordable than traditional benchtop counterparts, opening doors for broader adoption in resource-limited settings. However, the author notes that some manufacturers integrate these devices with proprietary online software, driving up costs and potentially hindering widespread use (5).

NIR spectrometers have two primary approaches in forensic analysis, the research team delves into both. The first approach focuses on detecting food adulteration, where authentic and adulterated samples are analyzed using chemometric models (5). These models classify samples based on spectral data and estimate adulterant concentrations with a high degree of accuracy, especially when adulterant levels exceed 5% by mass (5). While effective, this method's reliability depends on the availability of diverse and representative sample sets (5).

The second approach NIR spectrometers have is determining the provenance of food products. By analyzing spectral data, forensic scientists can classify samples based on their geographical origin or farming practices (5). To differentiate between products from different regions, researchers also use classifiers like partial least squares discriminant analysis (PLS-DA) and linear discriminant analysis (LDA) (5).

However, there are challenges associated with compact NIR instruments. Some of these challenges emerge when analyzing complex samples. For example, there is still a question whether portable NIR spectrometers have the capabilities in selectivity and sensitivity to conduct accurate and efficient analysis of forensic samples (5).

In the article, Pasquino emphasized the importance of adopting probabilistic rather than deterministic classification methods to mitigate the risks of false positives and negatives (5). In cases where samples cannot be confidently classified, they should be forwarded to laboratories equipped with more sensitive techniques for further analysis (5).

Portable NIR spectrometers offer significant benefits. The biggest advantage of portable spectrometers is that allows the analyst to conduct their work at the scene instead of transporting the samples to a laboratory. This on-the-ground analysis reduces the need for chemical reagents and enabling rapid, on-site decision-making (5).

However, achieving this vision requires collaboration between researchers and manufacturers. Pasquino underscored the need for affordable devices and open-access data acquisition software to foster innovation in data treatment and forensic method development (5).

Portable instrumentation is in high demand in the industry, and that is a trend expected to continue in the future. As technology advances, the accuracy and reliability of these devices are expected to improve, further minimizing the risk of misclassification (5).

The ability to perform rapid, non-invasive analysis in the field marks a significant milestone in forensic science. By overcoming current limitations and fostering collaboration, compact NIR spectrometers are changing how forensic investigations are conducted, and that is helping to bring about more efficient criminal investigations.

References

1. Wetzel, W. The Future of Forensic Analysis: Under the Magnifying Glass With the Experts. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/the-future-of-forensic-analysis-under-the-magnifying-glass-with-the-experts (accessed 2024-12-19).
2. Wetzel, W. Portable Spectroscopy and Forensic Analysis: Trends and Emerging Technologies. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/portable-spectroscopy-and-forensic-analysis-trends-and-emerging-technologies (accessed 2024-12-19).
3. Wetzel, W. The Future of Forensic Analysis: An Interview with Brooke Kammrath. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/the-future-of-forensic-analysis-an-interview-with-brooke-kammrath (accessed 2024-12-19).
4. Wetzel, W. Mass Spectrometry for Forensic Analysis: An Interview with Glen Jackson. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/mass-spectrometry-for-forensic-analysis-an-interview-with-glen-jackson (accessed 2024-12-19).
5. Foli, L. P.; Hespanhol, M. C.; Cruz, K. A. M. L.; Pasquini, C. Miniaturized Near-Infrared Spectrophotometers in Forensic Analytical Science − A Critical Review. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2024, 315, 124297. DOI: 10.1016/j.saa.2024.124297