Volume 31, Issue 4 (October 1986)
Color Comparison in Questioned Document Examination Using Microspectrophotometry
The work of the document examiner is often aided through the use of specialized analytical instruments. One such instrument, in use at the Immigration & Naturalization Service Forensic Document Laboratory (INSFDL), is the Nanometrics 10S Microspectrophotometer, manufactured by Nanometrics, Inc., of Sunnyvale, CA. This pseudo-dual-beam spectrophotometer performs nondestructive color analysis of objects down to 2 μm in size. First, an object to be examined (such as an ink line) is viewed through a microscope and the light reflected from it is measured over the visible spectrum. The reflected energy is then compared with a standard stored in the system's microprocessor, and a spectral curve is provided which is characteristic of the color of the object examined. At INSFDL, the Nanospec 10S™ has been successfully used to differentiate similarly colored printing inks, stamp pad inks, and fibers found on various travel and identity documents. Examples from recent cases will be demonstrated.