NCJ Number
219229
Journal
Forensic Science Communications Volume: 9 Issue: 2 Dated: April 2007 Pages: 1-6
Date Published
April 2007
Length
6 pages
Annotation
This paper uses case studies in order to illustrate the potential of X-ray diffractometry in enhancing the evidential value of nonpowder samples.
Abstract
The cases show that the information obtained from X-ray diffractometry is unique and that the X-ray diffraction pattern also can be used directly as a signature of the material for comparison when the chemical structure of the material is complex. X-ray diffraction (XRD) techniques have long been used for characterizing a wide variety of substances and are typically nondestructive methods of investigation. Among the various XRD techniques, X-ray powder diffraction is relatively simple and is commonly used for the analysis of powder samples; however, this technique has seldom been used for the analysis of nonpowder samples because of the form and size of most crime samples, the limited amount of material, and requirements for the preservation of samples. In one case study presented, the XRD technique was used to characterize the constituent fibers of a fabric. Textile fibers are a mixture of crystalline and amorphous regions. The extent to which either region predominates within the fibers largely determines the overall properties of the fiber. X-ray diffractometry was used to measure the degree of crystallinity in the fiber sample. Because no previous study that used the XRD technique was identified by the authors, a database of X-ray diffractograms of known fibers was created for comparison and identification of unknown fiber diffractograms. In the second case study, XRD showed its ability to characterize lipstick stains on cloth materials for initial screening. Because no previous study using the XRD technique was identified by the authors, a database was created that contained X-ray diffractograms of lipstick stains from known sources. 10 references