Criminal Forensic Analysis Chapter 1

Study Notes

Physical evidence can be individual characteristics (e.g., fingerprints and handwriting) or class characteristics (e.g., fibers and copy toners).
Common fibers (e.g., blue or white cotton from jeans or shirts) have little evidential value, but unusual fibers have more significant value due to their rarity.

IR spectroscopy can identify drugs and related chemicals using the computerized IR drug library at the Georgia Bureau of Investigation.
The library contains over 2000 spectra of drugs and related chemicals.
Ephedrine and pseudoephedrine have distinct spectral features between 1000 and 1300 cm-1, allowing for identification.
The reduction reaction of ephedrine/pseudoephedrine to methamphetamine removes the –OH group attached to the carbon next to the phenyl group.

IR spectroscopy can provide valuable information about the composition of a document.
Applications of IR spectroscopy in document examination include:
- Ink analysis: different types of inks have unique spectral fingerprints.
- Paper analysis: different types of paper have unique spectral fingerprints.
- Adhesive analysis: different types of adhesives have unique spectral fingerprints.
- Alteration detection: IR spectroscopy can detect alterations made to a document.

Raman spectroscopy has attracted interest in drug analysis due to its ability to analyze drugs without sample preparation.
Direct laser excitation methods enable rapid analysis of drug samples in plastic bags or bottles.

Forensic spectral imaging applications involve developing ridge patterns of latent fingerprints using IR spectroscopy.
This non-invasive method does not require chemicals, preserving any trace evidence within the area of the print.
IR spectroscopic regions can develop images of latent fingerprints, allowing for component analysis (e.g., oil, protein, and particulate matter).