NCJ Number
225616
Journal
Journal of Forensic Sciences Volume: 53 Issue: 6 Dated: November 2008 Pages: 1458-1467
Date Published
November 2008
Length
10 pages
Annotation
This study examined the potential of attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectral imaging as a technique for determining the sequence of heterogeneous line intersections produced with ballpoint pens and laser printers.
Abstract
The infrared spectral imaging technique, using a ZnSe ATR crystal in the large sampling accessory, was successful in determining the sequence of intersecting ballpoint pen and laser printer lines. By imaging at characteristic frequencies, it was possible to form spectral images that showed the spatial distribution of the materials. By examining the spectral images from the inks, it was possible to determine whether the ink was above or below the toner. In blind testing, ATR-FTIR spectral imaging results were directly compared to those obtained by eight experienced forensic document examiners, who used methods regularly employed in casework. ATR-FTIR spectral imaging achieved a 100-percent success rate in the blind tests; whereas, some incorrect sequence determinations were made by the document examiners. The primary advantages of this technique are that it is an objective method of analysis and relies on chemical differences in the samples rather than visual differences based on human interpretation. The technique is relatively fast, requiring only 6 minutes to analyze a sample; and it is nondestructive if the document can be maneuvered to place the line-crossing of interest in contact with the ATR crystal. The disadvantages of the technique are its inability to image a number of writing/printing materials on paper, including ink-jet printing and various pens, such as gel pens, roller ball pens, and felt-tip pens. Also, the instrumental requirements are more demanding than infrared microscopic imaging. A variety of writing/printing materials were used to produce homogeneous and heterogeneous intersecting-line samples, including black ballpoint pens, gel pens, roller ball pens, felt-tip pens, and laser and ink-jet printers. 6 tables, 8 figures, and 27 references