Gathering Evidence by IR and Raman Spectroscopy

Importance of the Topic

Forensic investigations rely on rapid and reliable identification of unknown materials to support law enforcement, public safety, and judicial processes.
Infrared and Raman spectroscopy offer non-destructive analysis with molecular specificity, enabling detailed characterization of illicit substances, trace evidence, and questioned documents.

Objectives and Overview

This summary reviews the role of FT-IR and Raman spectroscopic methods in forensic analysis, highlighting:

• Identification of drugs, explosives, and chemical hazards
• Characterization of trace evidence (fibers, particles, paint layers)
• Detection of forgeries in currency, documents, and artwork

Methodology and Instrumentation

IR spectroscopy generates molecular fingerprints by measuring vibrational modes of organic and inorganic compounds, facilitating compound identification and quantification.
Raman spectroscopy complements IR by providing high specificity, non-invasive analysis of pigments and materials within packaging or glass.
Advanced instrumentation includes:

• ALPHA-P FT-IR spectrometer for quick field and lab analyses
• LUMOS FT-IR microscope for microspectroscopic mapping down to the micrometer scale
• HYPERION 3000 FT-IR imaging microscope with FPA detector for rapid chemical imaging
• SENTERRA Raman microscope for high-precision pigment analysis and continuous calibration

Main Results and Discussion

Drug samples, including street mixtures, were identified within seconds; mixture analysis revealed cocaine free base adulterated with benzocaine and phenacetine.
Plastic explosives (e.g., NSP711 composed of PETN and plasticizer) were accurately distinguished using FT-IR.
Mobile deployment with battery operation and intuitive software enables on-site analysis by non-specialists.
Microspectroscopic techniques identified polymer types in 25 µm fibers and deconvoluted multilayered paint chips, producing detailed chemical images of layer distributions.
Automated FT-IR mapping differentiated altered inks in a forged document, and Raman microscopy characterized pigments in historical artwork.

Benefits and Practical Applications

These spectroscopic methods offer rapid, reproducible, and non-destructive analysis with minimal sample preparation, suitable for both laboratory and field use.
The ability to analyze micro-samples and obtain chemical images enhances the investigation of complex, heterogeneous evidence.

Future Trends and Potential Applications

Integration of machine learning and expanded spectral libraries will improve mixture deconvolution and unknown substance identification.
Miniaturized, portable systems with wireless data transfer will further enable real-time on-site forensics.
Advances in hyperspectral imaging and coupling with complementary techniques (e.g., ion mobility) will expand detection sensitivity and selectivity.

Conclusion

FT-IR and Raman spectroscopy constitute powerful, complementary tools in forensic analysis, delivering fast and detailed material characterization across diverse sample types.
The continual development of instrumentation, software, and spectral databases promises to enhance investigative capabilities and support justice processes effectively.

Used Instrumentation

• ALPHA-P FT-IR spectrometer
• LUMOS FT-IR microscope
• HYPERION 3000 FT-IR imaging microscope
• SENTERRA Raman microscope
• ATR crystals, FPA detectors, OPUS software