Analytical Techniques for Elemental Characterization in Forensic Evidence

Elemental characterisation underpins the forensic identification and comparison of a wide range of materials, from glass fragments to polymer residues. Techniques such as X-ray fluorescence (XRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) enable non-destructive or minimally destructive probing of trace elements, providing chemical “fingerprints” that can link evidence to specific sources. Complementary methods, including particle-induced X-ray emission (PIXE), scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS) and prompt gamma-ray activation analysis (PGAA), extend the detectable elemental suite and enhance sensitivity for light or heavy elements. Advances in sample preparation, calibration standards and data processing have improved quantification, reproducibility and inter-laboratory comparability. Moreover, the integration of multivariate statistics and machine learning classification models has begun to address the variability inherent in measurements obtained from different instruments and laboratories. Together, these developments are broadening the scope and reliability of elemental profiling in casework, facilitating discrimination between materials of similar appearance and assisting in establishing links between crime scenes, suspects and victims on a global scale.

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Analytical Techniques for Elemental Characterization in Forensic Evidence publication trend

The graph below shows the total number of articles in analytical techniques for elemental characterization in forensic evidence across all publications each year (not limited to Nature Index journals).

Technical terms

X-ray fluorescence (XRF): A non-destructive technique that excites atoms with X-rays to induce characteristic secondary emissions, enabling elemental identification and quantification.

LA-ICP-MS: Laser ablation inductively coupled plasma mass spectrometry; a method in which a pulsed laser removes microscopic material for introduction into a plasma source, where ionised atoms are analysed by mass spectrometry.

PIXE: Particle-induced X-ray emission; an ion beam irradiates a sample to stimulate X-ray emission from constituent elements, offering high sensitivity for light elements.

SEM-EDS: Scanning electron microscopy with energy-dispersive X-ray spectrometry; a combined imaging and analytical technique that identifies elemental composition at micron-scale resolution.

LA-ICP-TOF-MS: Laser ablation inductively coupled plasma time-of-flight mass spectrometry; an extension of LA-ICP-MS that employs a time-of-flight analyser for simultaneous detection of all mass channels, improving speed and throughput.

References

1. A novel standard for forensic elemental profiling of polymers by LA-ICP-TOF-MS. Forensic Chemistry (2023).
2. Evaluating the strength of evidence of elemental profiling of polymers with LA-ICP-MS. Forensic Chemistry (2024).
3. Toward Developing TechniquesAgnostic Machine Learning Classification Models for Forensically Relevant Glass Fragments. Journal of Chemical Information and Modeling (2022).