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Validation of LAB Color Mode as a Nondestructive Method To Differentiate Black Ballpoint Pen Inks

NCJ Number
Journal of Forensic Sciences Volume: 52 Issue: 4 Dated: July 2007 Pages: 967-973
Derek L. Hammond B.A.
Date Published
July 2007
7 pages
This study tested the validity and reliability of nondestructive digital processing methods, such as lab color mode (available in Adobe Photoshop), as alternative methods for forensic document examiners to use when attempting to differentiate writing instrument inks.
The study determined that lab color mode is a valid and reliable method for nondestructively differentiating black ballpoint pen inks. In addition, lab color mode was able to differentiate a significant number of pen-pair samples that traditional infrared techniques could not distinguish. Traditional infrared examination methods that used the VSC-4C, however, were able to differentiate a significant number of pen-pair samples that the lab color mode technique could not distinguish. The findings show the value of each technique and provide support for the recommendation that forensic document examiners use both methods if the initial method used is unable to distinguish between the samples examined. In the current study, 44 black ballpoint ink pens were used to create 990 pen-pair samples for analysis by using established lab color mode techniques. Following the 1-3-day "drying" period, each sample was scanned at 300 pixels per inch with a calibrated UMAX PowerLook 2100XL flat-bed scanner. The RGB images were saved as .tiff files. Adobe Photoshop CS was opened and a "batch command" was used to process all of the previously scanned and saved images. Immediately following lab color mode processing, each original pen-pair sample was subjected to infrared examination with a Foster & Freeman Video Spectral Comparator (VSC)-4C in accordance with the instructions in the manufacturer's User Guide. 3 tables, 9 figures, and 7 references