NCJ Number
210786
Journal
Journal of Forensic Sciences Volume: 50 Issue: 4 Dated: July 2005 Pages: 915-923
Date Published
July 2005
Length
9 pages
Annotation
This study examined the feasibility of identifying spur marks (tool marks created by the spur gears of many inkjet printers) on inkjet-printed documents for the purpose of linking questioned documents with suspect inkjet printers.
Abstract
The spur gears hold the paper in place as it passes through an inkjet printer. They are located in front of the print heads and run over the top of the document. Spur marks are the indented marks left on the paper by the spur gears as the paper passes through the inkjet printer. The spur marks found on questioned documents and the spur gears of suspect printers can be compared to determine whether they match. Two printers of different models and manufacturers were used in this experiment. Reference spur marks from each printer were sampled on a pressure measurement sheet attached to a sheet of plain copy paper. The sheet was fed through the paper conveyance system without printing an image. The color of the paper changed to magenta in areas in which pressure was induced, and the density of the color indicated the magnitude of the pressure. Reference spur marks were digitized at 600 dpi using a flatbed scanner. Spur marks on the printout were visualized by oblique lighting from an incandescent light source, and the locations of spur marks were recorded in an image data file. Thereafter, the pitch and mutual distance of spur marks were measured with a glass scale. The spur marks on the printout and the reference specimens were compared. The spur marks on a printout matched the reference spur marks within 3 percent of the measured values. Thus, spur marks were determined to be effective class characteristics in identifying certain brands of inkjet printers. 16 figures, 6 tables, and 16 references