Trace evidence

This type of evidence is usually not visible to the naked eye and requires specific tools and techniques to be located and obtained.

[5] Since then, forensic scientists use trace evidence to reconstruct crimes and to describe the people, places, and things involved in them.

Studies of homicides published in the forensic science literature show how trace evidence is used to solve crimes.

Trace evidence is found in many different forms with some examples including, but not limited, to fire debris, gunshot residue, glass fragments, and fibres.

"Witness marks" are also an important form of trace evidence, especially in engineering and may be critical in understanding how a product failed.

[6] As for the recovery of the evidence, samples may be collected by handpicking, tape lifts, combing, or removal of an entire object.

It is also important to note that great care must be taken to prevent contamination of the evidence with other substances (such as natural oil and sweat on the hand of the collector).

The Scientific Working Group Materials Analysis (SWGMAT) has created guidelines to ensure proper protection and collection of trace evidence.

[9] The Federal Bureau of Investigation (FBI), has even implemented these standards into their work revolving trace evidence.

False positives and contamination by subsequent handling or nearby objects (e.g. mixing of blood from victim and attacker), are problems of many common substances and the necessity of human involvement in the collection of trace evidence.

Both can occur with DNA traces and fingerprints, and therefore evidence should be collected, analyzed, and presented in accordance with established guidelines.

No standards and methodologies have been created to determine physical fit between two piece of evidence and consistency of work conducted from various analysts.

[17] The Organization of Scientific Area Committees (OSAC) have clarified that future research must be conducted to create methods for quality of fit and error rates.