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Case Report
Introduction
Vehicle forgery (i.e., vehicles whose engine numbers, chassis numbers, or other identifying marks have been obliterated and subsequently restamped or painted with false numbers) is a common occurrence in all countries in the world. If a stolen and renumbered vehicle is involved in a crime (e.g., murder, sexual assault, robbery, theft, etc.), then it becomes necessary to restore the original numbers to prove the identity of the motor vehicle [1-5]. The information may be used for establishing the ownership of the stolen motor vehicle or, in some cases, to trace the crime [5].
When a number is stamped into a metal surface with a punch or a die, the crystalline structure of the metal in the area of the stamp is disturbed. This disturbance penetrates for an appreciable distance into the substance of the metal. These disturbances remain even after the actual marks caused by the punch have been visibly erased by filing or other means. When suitable chemical reagents are applied to such erased areas, the evidence of the disturbance in the crystalline structure becomes temporarily visible. The etching solutions act more readily on the undisturbed areas of the metal than on the compressed particles. Thus, by the application of suitable chemical solutions, it is possible to redevelop numbers that have been filed off [1].
This article describes two cases involving the successful restoration of obliterated original numbers in motor vehicles, eventually leading to the solution of the crimes.
Motor Vehicle Examination Procedure
The procedure we used in the examination of the two cases involving steel surfaces to be described in this article is as follows [1-4]:
1. After removing dirt and oil, the metal surface undergoing obliteration was examined. Any digits or parts of them, if visible, were noted.
2. Using emery paper, the surface was rubbed down until a reasonably smooth surface was obtained. We found that this procedure brought good results. Any digits appearing at this stage were noted.
3. The surface was then cleaned with acetone to remove all traces of oil, grease, or paint. The surface was not touched, because fingerprint deposits would affect the restoration process.
4. The surface was then swabbed for about two minutes with cotton wool using Fry's reagent (crystalline...