Obliterated Serial Number Recovery on Materials with Laser Imprinting in the Absence of Plastic Deformity

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Student Presentation

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Faculty Sponsor

Dale Russell


In the field of forensics the recovery of serial numbers that have been removed or obliterated is a key analytical technique to investigations. Most serial numbers are imprinted by stamping the metal with force; this disrupts the metal crystalline structure beneath the imprinted numbers. This damaged crystalline layer beneath the imprinted numbers is called plastic deformation and is the key to recovering the numbers after obliteration. A number of methods are available for recovering such numbers. However, laser etching is becoming a more popular way to imprint numbers onto materials, and this makes recovery of the numbers much more difficult because laser etching does not leave any known plastic deformity. There is a need in forensic science for a method to recover obliterated, laser etched serial numbers. The hypothesis of this research is that laser etching will leave detectable changes arising from applying heat (the laser) in an oxidizing atmosphere (air). Reflectance FTIR and Raman spectroscopic methods are used to examine the surface for oxidative chemical changes. These are detectable as changes in vibrational modes with incorporation of oxygen into the perimeter of the imprinted area.

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