Crime Scene Investigation & Forensic Science
Although crime scene investigation has come a long way since the days of Sherlock Holmes, careful examination of evidence still remains important today! The science that deals with crime scene investigation, or science that is applied to law cases, is called forensic science.
Evidence Collection
There is usually only one opportunity to obtain evidence from a crime scene, therefore the investigation must be methodical and complete. Evidence that might have been touched or microscopically contaminated by the suspect(s) must be identified and collected including very small items such as fibers, dirt, and dust.
Evidence Collection includes:
- Preliminary searches
- Photographs and video footage
- Careful measurements and detailed notes and sketches
- Packaging and cataloguing of all evidence
- The use of laser and alternative-light sources that reveal latent fingerprints, stains, hairs, fibers
- The use of Luminol to see traces of blood that has been cleaned or concealed
- Analysis of blood stains and patterns to understand how the crime took place
Let's take a closer look
TYPES OF FORENSICS ANALYSIS
Hair and Fiber
Although a single hair or fiber cannot place a suspect at a crime scene, collections of hair or fiber can be used to establish with a high degree of probability that the suspect is connected to the crime.
Hairs have patterns that can indicate a person's race and what diseases he may have. If the hair has any follicular material or blood on it, a DNA test can performed for even more specific results.
Toxicology
Toxicologists examine blood and tissues to discover the presence and quantity of drugs or poisons in a person’s body. Toxicological reports can assist investigators by showing whether the drug ingested was fatal and the approximate time the drug was introduced into the body. Toxicology was first systematized by the Spanish physician Matthieu Orfila (1787–1853).
Serology
Serology is the study of serums such as blood and other human fluids. In 1915, the Italian scientist, Leone Lattes developed a simple test that determined the blood type of a dried bloodstain. Further developments increased the sensitivity and accuracy of these tests, identifying over 100 different blood factors. These factors are used to compare blood samples from suspects. If the combination of blood factors differ, that person would be less likely be the perpetrator.
The addition of DNA analysis allows investigators to detect identifying characteristics of body fluids and cells with great precision, making it easier for them to implicate or eliminate potential suspects.
Document Examination
Forensic document examination includes handwriting and typewriting identification, age determination, and determining the sequence of events involved in a document’s preparation, handling, or alteration.
When the perpetrator makes a careful drawing of the victim’s signature or traces an authentic signature, the forgery can be exposed but cannot be identified as the handwriting of the perpetrator.
Where the paper was made is just as important. To do this fibers, fillers, and sizing must be examined. Techniques used in this process include staining and microscopic examination, X-ray diffraction , and chemical tests. The chemical analysis makes it possible to identify paper by batches meaning it would tell the date, time, and location of when the paper was manufactured.
Firearms and Tool Marks
Each firearm leaves individual markings on a bullet and case when it is fired. Such markings can be used to determine whether evidentiary bullets were fired from a suspects weapon. Similar techniques are applied to marks left behind at crime scenes by pry bars, screwdrivers, and other tools.
Careers in Crime Scene Investigation
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