Forensic Chemistry - Methods - Sample Integrity

Sample Integrity

Forensic chemists usually perform their analytical work in a sterile laboratory decreasing the risk of sample contamination. In order to prevent tampering, forensic chemists must keep track of a chain of custody for each sample. A chain of custody is a document that stays with the evidence at all times. Among other information, contains signatures and identification of all the people involved in transport, storage and analysis of the evidence.

This makes it much more difficult for intentional tampering to occur, it also acts as a detailed record of the location of the evidence at all times for record keeping purposes. It increases the reliability of a forensic chemist's work and increases the strength of the evidence in court.

A distinction is made between destructive and non-destructive analytical methods. Destructive methods involve taking a sample from the object of interest, and so injures the object. Most spectroscopic techniques fall into this category. By contrast, a non-destructive method conserves the integrity of the object, and is generally preferred by forensic examiners. For example, optical microscopy and microspectroscopy cannot injure the sample, so they are considered non-destructive techniques.