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Dimensional Review of Scales for Forensic Photography

NCJ Number
Date Published
March 2016
11 pages
Since the ABFO No. 2 Standard Reference Scale (1) is used by the forensic science community as an accurate reference scale for photography, this study examined the overall accuracy of this scale’s major centimeter graduations, internal/external diameters of the circles, error in placement of the circle centers, and leg perpendicularity.
Four vendors were selected for the scales, and the features were measured on a vision-based coordinate measurement system. The scales were well within the specified tolerance for the length graduations. After 4 years, the same scales were measured to determine what change could be measured. The scales demonstrated acceptable stability in the scale length and center-to-center measurements; however, the perpendicularity exhibited change. The study results indicate that scale quality checks using certified metal rulers are good practice. (Publisher abstract modified)

Date Published: March 1, 2016