Importance of Trace Evidence in Forensics

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Importance of Trace Evidence in Forensics
A crime scene investigator picking out trace evidence from the crime scene

Trace evidence is the microscopic material which are found on the crime scene and which have great significance in solving criminal cases. These are very small in nature which can’t be seen by naked eyes sometimes and can be transfered from one place to another very easily.

Each and every contact leaves behind a trace and hence a person can be linked/unlinked to being present at a particular place.

Trace evidence is also known as “silent witness”. Trace evidence links a culprit to crime scene, or  things involved. Trace evidence is found in many forms from as large as brick to as small as hair strand. It can be used to investigate every type of crimes from rape to terrorist attack.

Trace evidence characterize a particular environment there will be infinitesimally correlation between the evidences of different environment. Typically trace evidences include hair, fibres, bloodstains, paint, glass pieces, gunshot residues, body fluids etc. It plays an important role in identification of any type of crime.

Types of Trace Evidence

Depending on the nature of crime different amount of traces are found at crime scene that correlates victim, perpetrator and environment. Environment in this case means either the natural or the precise location of the crime. Different types of evidences are found however the common examples are:

  • Hair
  • Paint
  • Glass
  • Fibers
  • Soil
  • Fire debris
  • Body fluids
  • Chemical residues

1. Hair

Hair is a characteristic feature of all mammals including human. It is an integral part of the skin derived from the epidermis of the skin. A human hair can be connected with a specific racial group grounded on recognized prototypes for every group. Forensic expert distinguish between hair of animal and human.

Forensic scientists distinguish six types of hair on the human body i.e.,

  • Head hair
  • Eyebrows and eyelashes
  • Beard and mustache hair
  • Underarm hair
  • Auxiliary or body hair Pubic hair.

Hair also helps in differentiating between sex of human. Male hairs are Coarser, darker, thicker and female hair is long, fine and silky. Hair also includes Human DNA that helps in concluding if a particular strand belongs to a suspect or not.

2. Paint

Paint is found at crime scene and is generally transferred from one place to another through the suspect. Paint chips are generally found in hit-and-run and burglary cases. It is used to compare the vehicle involved in the incident. Paint chips from burglary tools can be used to determine whether the tool is used in a crime or not. In assault cases, paint can be used as sometime paint is left at the crime scene and the weapon consisting of paint could be found at suspect’s home.

3. Glass

Glass plays an important role as a trace evidence in cases of arson, hit and run, burglary and theft. Glass that has been broken or fragmented at a crime scene is crucial forensic evidence found. In theft cases broken window pieces are found, glass fractures are seen in gunshot cases. Through which we can identify the direction of bullet shot. Density method is used to compare the glass to observe the origin of glass.

4. Soil

Soil can provide important information during criminal investigations as transfer evidence because many criminal cases take place under circumstances such that soil transfers to a criminal or victim. The variation in soils from place to place makes soil valuable evidence to prove linkage between a suspect and a crime scene. Texture of soil varies from place to place.

5. Fire Debris

The basic role of an investigator at a fire scene is twofold: firstly to determine the origin of the fire (the site where the fire began), and secondly to examine closely the site of origin to try and determine what it was that caused a fire to start at or around that location.

An examination would typically begin by trying to gain an overall impression of the site and the fire damage; this could be done at ground level or from an elevated position. From this, one might proceed to an examination of the materials present, the fuel load, and the state of the debris at various places.

6. Body Fluids  

Body fluid traces recovered at crime scenes are among the most important types of evidence to forensic investigators. They contain valuable DNA evidence which can identify a suspect or victim as well as exonerate an innocent individual.

The first step of identifying a particular body fluid is highly important since the nature of the fluid is itself very informative to the investigation, and the destructive nature of a screening test must be considered when only a small amount of material is available.

Importance of Trace Evidence

  • Since they are smaller in size and almost invisible to naked eye, remains hidden from the culprit to later help in investigation.
  • Provides vital link between the crime, suspect and the victim.
  • Helps in confirming the theory of the investigators.
  • Helps in matching the original origin of the evidence with accuracy for clear ideas during investigation.
  • Also helps in reconstructing the crime scene.
  • May provide a clear information about the suspect(s).
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