trace evidence
TRACE EVIDENCE AS AN IMPORTANT TOOL UNDER FORENSIC SCIENCE
Introduction
Edmond Locard, founder of the Institute of Criminalistics at the University of Lyon, France, developed what has become known as Locard’s Exchange Principle. This states that “every contact leaves a trace”, implying that a criminal will leave trace and take away trace evidence when at a crime scene. Trace evidence often refers to minute samples of a substance, particularly fibres, hairs, glass fragments and paint chips. Crime scenes will commonly contain trace evidence, often caused by the perpetrator unconsciously coming into contact with surfaces and leaving behind or picking up particulates.
Trace evidence is created when objects contact. Material is often transferred by heat induced by contact friction. The importance of trace evidence in criminal investigations was shown by Dr. Edmond Locard in the early 20th Century. 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 important in accident investigation, where movement of one part against another will often leave a tell-tale mark. Such analysis is of great use in forensic engineering.
The presence of trace evidence is particularly dependent on its persistence, as some particles and substances will remain on a surface more readily and for a longer period of time than others. The amount of time evidence will persist for depends on the size and shape of the particle, the amount deposited, activity between deposition and recovery, the nature of the environment, and the amount of time passed. Small particles will persist for longer than larger particles, as they are more likely to become lodged in the surface material. Irregular surfaces, such as certain fabrics and wood, will collect particulates more readily than
Introduction
Edmond Locard, founder of the Institute of Criminalistics at the University of Lyon, France, developed what has become known as Locard’s Exchange Principle. This states that “every contact leaves a trace”, implying that a criminal will leave trace and take away trace evidence when at a crime scene. Trace evidence often refers to minute samples of a substance, particularly fibres, hairs, glass fragments and paint chips. Crime scenes will commonly contain trace evidence, often caused by the perpetrator unconsciously coming into contact with surfaces and leaving behind or picking up particulates.
Trace evidence is created when objects contact. Material is often transferred by heat induced by contact friction. The importance of trace evidence in criminal investigations was shown by Dr. Edmond Locard in the early 20th Century. 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 important in accident investigation, where movement of one part against another will often leave a tell-tale mark. Such analysis is of great use in forensic engineering.
The presence of trace evidence is particularly dependent on its persistence, as some particles and substances will remain on a surface more readily and for a longer period of time than others. The amount of time evidence will persist for depends on the size and shape of the particle, the amount deposited, activity between deposition and recovery, the nature of the environment, and the amount of time passed. Small particles will persist for longer than larger particles, as they are more likely to become lodged in the surface material. Irregular surfaces, such as certain fabrics and wood, will collect particulates more readily than