Forensic document examination is the scientific analysis of document evidence in legal investigations. It tends to be applied most often in forgery cases, but can be used in any cases that have documents as evidence, such as suicide notes or ransom letters. Examiners study contracts, personal notes, or any other documents involved in an investigation to determine authenticity or ownership.
Handwriting identification is one of the most common forms of forensic document examination. It is based on the notion that individuals have unique writing characteristics, such as the slant of words or amount of pressure used while writing. To determine if a document is written by a suspect, an examiner uses magnifiers and microscopes to compare an existing handwriting sample with the document evidence. The writing sample must match the evidence type for an accurate comparison. For instance, cursive writing can only be compared with another cursive sample.
If the writer of a document is unknown, examiners are trained to recognize the characteristics of handwriting formation in order to come up with a suspect profile. They look for both class handwriting characteristics and individual handwriting characteristics. Class characteristics are handwriting traits that tend to be shared by certain groups, such as particular language groups or occupations. Individual characteristics are letter formations or writing styles that are unique to a specific writer.
Forensic document examination can aid in investigations by giving investigators an idea of the location and date a document was prepared. Examiners can study the paper and ink under a microscope to determine the type of typewriter, printer, or photocopier used. They can also identity the variety of ink. Although forensic document examiners can estimate the date a document was made by the condition of the paper or other physical clues, only an ink chemist can determine the precise date the ink was used.
Examiners also inspect documents for alterations or erasings. They can use a Video Spectral Comparator, a machine that shines the document with infrared light abd makes added or erased markings illuminate differently than the original writing. Alteration or erasing detection is often used in fraud cases in which dates or monetary amounts are changed on a contract or check. It can also be used in the instance of disputed consent forms to prove if a check mark was made at a different time than the document was filled out.
Forensic document examination can involve documents that do not have any visible markings. If a note was written on a pad or stack of papers, it leaves indentations in the other layers that are not easily seen by the naked eye. For instance, if a kidnapping suspect uses a notepad to write a ransom note, examiners can use an Electrostatic Detection Apparatus to create an image of the under layers of paper onto transparency film. Examiners can see if that particular notepad was the one used in the crime.