Serial Numbers and Fingerprints Quiz 3

Firearms, electronics, farm equipment, machinery, and vehicles.

Federal and state law make it a violation to alter or remove identifying data. Theft and illegal use of items cause offenders to remove this data so ownership cannot be traced.

Once metal has been stamped or impressed, the composition of it is changed forever due to the stress applied on the metal. This allows for serial number restoration.

A unique number applied to an object by a manufacturer. Unique number vary based on manufacturers by numeric or alpha characters.

Date stamp of manufacturer. Location of manufacturing. Sequence of manufacturing. Who the manufacturer is.

Firearms with obliterated serial numbers.

Quality Control: Identifies defective products. Unique Identity: Item individuality. Deterrent Against Theft: Assists in the possibility of recovering stolen items.

Can be applied by a variety of methods. Each method imparts unique characteristics that can be differentiated from one another. Manufacturers general use most economically efficient method for them.

Dot Matrix Engraving. Laser Engraving. Stamped Engraving

Shallow and are made by a rapid progression of dots.

Shallow and often show a burned appearance on the metal. Branding effect.

Most common type of engraving encountered in a crime lab. Made using a stamp that creates a positive impression on the object.

Occurs when serial number is stamped in metal. After force causing deformation is removed, the impression remains. An engineering term meaning “permanent deformation” or irreversible changes due to force.

Occurs due to the force or pressure applied to a surface of metal. Depth is dependent on the strain through the surface of the metal. Purpose of stamping is to impart a permanent impression on the metal.

The process of making a surface or object undecipherable by wearing away. Often occurs by grinding down most visible surface of serial number.

Grinding. Pinging. Over-stamping. Drilling. Welding.

Most common is chemical restoration. Others include: Non-destructive, bar code decryption (manual), automatic decoding.

Uses chemical etchants (acids) on the surface of smooth metal. Acidic ferric chloride mixture.

Serial numbers are viewed when they are acid etched due to specular reflection and diffuse reflection.

The ability to view the light reflecting off a smooth surface.

The ability to view light reflecting off a rough surface. This dark area that reveals number is result of diffuse reflection.

• Polish the surface (provides specular reflection and a consistent reflection of light. • Apply acid which will react with metal and produce hydrogen gas bubbles. • Documentation

Acid etching may restore serial number the first time, but if not the step can be repeated.

Accomplished by: Extensive note-taking. Chemicals used. Order of operations. Photographs.