Forensic Document Analysis – Looking for Distinctive Qualities in Paper Copies

Suppose crime scene investigator’s come upon document such as a ransom note or a suicide note that has been copied in an attempt to hide the offender’s handwriting, the ink he used, or typewritten text. How can they determine that this copied piece of paper came from a particular copy machine?

In this article, I will attempt to explain how forensic document analysts determine a link between a paper copy to the machine that produced the copy.

A copy machine has the ability to duplicate an image from one piece of paper onto another through a complex series of events. First of all, a lens focuses the image of the original paper onto what is known as a drum that is charged up with electrons and coated with selenium or some other substance that is sensitive to light. The image is then retained on the drum as the drum is coated with toner powder. The toner powder sticks to the surface of the drum in direct relation to the degree of strength of the electrostatic charge of the electrons. This toner image is then transcribed onto a blank piece of paper (or copy) which, in turn, is exposed to a fixing agent. A fixing agent is a chemical used to “attach” the toner powder permanently on the blank piece of paper.

For the purposes of forensic document analysis, criminal investigators can sometimes link a photocopied document to a particular copy machine by creating a comparison document to compare the photocopy against. This is due to the fact that the mechanisms inside the machine that pull the paper onto and remove it from the copy surface leave distinctive markings on the paper. Similarly, the camera lens, cover glass, or drum surface may have scratches, etches, or abnormalities that mark every copy that it creates. From time to time, these markings show up on copied paper. Forensic scientists can then identify and link this marked copy to the copier that created it and perhaps the perpetrator to the crime.

With advancing technology, forensic scientists have many tools in its bag of tricks to link a suspect to a crime.

Fabiola Castillo is an online marketer for the website NinjaCOPS SuperStore. This virtual store specializes in crime prevention tools where you can buy cheap stun guns, kubaton keychains, hidden video spy surveillance cameras, nunchaku training videos, hand Tasers, expandable steel batons, and many other personal safety products.

Author: Fabiola Castillo
Article Source:
Digital Camera News