Evidence Collection at a Crime Scene
Fingerprints, Ballistics, Hair and Fibers, Impression Evidence
Feb 4, 2009
Criminal prosecutions rely on evidence presented in a court of law. This means that, correctly collected, well preserved, and uncontaminated evidence is vital ensure a successful outcome.
Crime scene yellow tape is a familiar sight. Crime scenes are immediately sealed off, not only to prevent the public from seeing a gory sight, but also to prevent anyone, including police officers and other investigators from trampling the crime scene and contaminating the evidence.
Badly Compromised Crime Scene
An example of a badly compromised crime scene was that of Jon Benet Ramsey, the six-year-old beauty pageant contest who was brutally slain in her parents’ luxury home in Boulder Colorado on 26 December 1996.
Chain of Custody is Important
In order to preserve the integrity of the evidence of a crime scene, human contact should be avoided since even one or a few cells from skin can compromise the results.
It is very important to keep careful track of the chain of custody of each sample - the chain of custody is a list of date and times and locations of people who have handled the crime scene evidence.
Many Different Types of Evidence Collection
There are many different types of evidence that can be collected at a crime scene and to exclude or include people the investigators are interested in. As well as fingerprints and physical evidence like bodily fluids i.e., blood, saliva and semen there is also eyewitness testimony and impression evidence like tire tracks, tool marks and bite marks. Soil samples and insects can also be used if a body is found.
What is the First Thing a CSI Does at a Crime Scene?
After securing the crime scene, the Scenes of Crime Officers (SOCO) (UK) or Crime Scene Investigator (CSI) (USA) usually photograph the scene as well as video it. Sketches and diagrams are made if necessary. The latest forensic technology is a scanner that produces a 360 Degree image for the criminal investigators to study whenever they want to see where anything was positioned within the crime scene or if they want to do a crime scene reconstruction.
When involved in evidence collection, Investigating officers usually then put down numbered markers to indicate where any shell casings or bullets are located as well as any blood spatter evidence or other items that need to be photographed in position at the crime scene.
What other Evidence is Collected or Preserved at a Crime Scene?
- The most vulnerable evidence is collected first like hair, which could beblown away by the wind.
- Fibers are collected with tweezers and put into separate holding packets and labeled.
- In interior locations, carpets are vacuumed for trace evidence.
- Tire tracks are photographed and sometimes casts or moulds are made
- Swabs are collected of blood, tissue and other matter for DNA
- Latent prints are taken where they can at the crime scene and other items are removed to be fingerprinted in the lab.
- Ballistic evidence.
Trace Evidence Detection with Ultra Violet and Infra Red Lights
Ultraviolet and infra red lights are often used to find trace evidence at crime scenes, but no matter how basic or sophisticated the evidence collection techniques are, all CSI technicians or crime scene specialists need to ensure at all times that they maintain a clean crime scene and keep the evidence uncontaminated.
Sources:
Hairs, Fibers, Crime, and Evidence Part 1: Hair Evidence by Douglas W. Deedrick Unit Chief, Trace Evidence Unit, Federal Bureau of Investigation Washington, DC.
Crime and Forensics - Collecting the Evidence - Discovery Channel.
 |
 |
