Raising the Numbers
Written by Ed Staley   

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Raising the numbers:
Restoring Altered VINs or Serial Numbers

TAMPERING with the Vehicle Identification Number (VIN) on a vehicle or the parts of a vehicle is clearly an illegal act. For decades,

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Figure 3

however, criminals have sought ways to change them, grind them down or just plain remove them (Figure 1).

Law-enforcement officers have continued to struggle with altered identities of stolen property, and have worked to establish methods to recover VINs and serial numbers stamped into the frames of property.

The serial number on items such as motor vehicles, firearms, bicycles, and motorcycles are commonly removed or altered in an attempt to prevent the identification of the item’s original owner. The serial number can sometimes be restored depending on the degree of obliteration or alteration.

When a number is stamped into a metal object, the metal underneath the number is compressed and hardened. Even when the number is ground off, this hardened area may still be present. By applying an acid solution, the metal can be slowly eaten away and the number may reappear. This is commonly referred to as “raising the serial number”.

By restoring an obliterated or altered serial number, an object can possibly be traced and returned to its original owner, or may link a suspect to a crime scene.

The process

Begin the process in a clean and well-ventilated area. Care should be taken to set up photography equipment prior to the etching process. The etching process should be monitored and photographed at various stages, as the entire process could take up to several hours.

It is recommended that all spurious marks be removed from the surface before any attempt is made to restore the VIN or serial number. The surface should be brought to a high-gloss finish, even if some irregularities exist. The use of sandpaper or an emery cloth in 320, 400, and 600 grit is recommended to achieve the glossy finish.

Use a cleaning solvent to remove all traces of oils, grease, or other substances that will prolong the etching process. Alcohol, acetone, methyl ethyl keytone (MEK), carbon tetrachloride, and gasoline all provide good results.

The etching reagent our agency currently uses is a modified Fry’s reagent that is comprised of concentrated hydrochloric acid, distilled water, and crystalline cupric chloride. The reagent is made in a controlled laboratory environment where it is commonly used to recover serial numbers that have been removed from firearms.

Using a cotton swab, apply the reagent to the polished area slowly, in a back-and-forth motion over the surface. It is not necessary to apply pressure to the surface. Swabs comprised of cotton batting rolled onto applicator sticks (such as those found in laboratories) make suitable swabs for applying the reagent.

Under certain circumstances, it may become necessary to confine the reagent to a specific area. This can be done by constructing a dam completely around the area using products such as Mikrosil or AccuTrans, forming a dam no more than 0.25-inch high (Figure 2).

Monitor the progress of the etching process to ensure the quality of the characters that appear and be ready to stop and neutralize the etching by flushing with water.

Capturing the characters

Photography is one of the easiest ways to capture and document the characters once they have been recovered. The use of a tripod and remote shutter release will ensure a much better quality photograph (Figure 3). The use of a scale in the photograph will provide the appropriate documentation needed. Oblique lighting usually serves as the best method to illuminate the characters for your photograph.

Once the characters have been raised and your photographs have been taken, a simple modeling clay can be used to make a cast or impression of the VIN number. Then apply a product such as Mikrosil or AccuTrans against the modeling clay and allow it to cure. The result is a complete replica of the numbers that were raised from the damaged plate. The numbers and photographs can then be secured as evidence.

In addition to the chemical etching process, electricity can be used to expedite the process. Making the surface the positive pole of a low DC circuit (a 6- or 12-volt battery), and using the swab as a cathode or negative pole markedly speeds up the metal removal. This process is best applied to harder steels such as motorcycle and vehicle frames.

About the Author

Ed Staley is a special agent with the Ohio Bureau of Criminal Identification & Investigation, a division of the Attorney General’s Office. His assignment is to the Crime Scene Unit in the Northeast Region. The unit provides crime-scene assistance throughout the state. Staley can be reached at: 330-659-4600 or by e-mail at: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

"Raising the Numbers," written by Ed Staley
September-October 2010 (Volume 8, Number 5)
Evidence Technology Magazine
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