This is the perfect answer to AC 1.3, for year 12/13 Criminology students. The AC is worth 6 marks, this answer will get you all the marks possible for this question.
Locard's exchange principle states every contact leaves a trace, this means that material
from the crime scene will be present on the offender. This principle emphasises the
importance of finding and processing evidence as it can be crucial in charging a suspect with
a crime. There are two types of evidence collected in criminal investigations: physical
evidence and testimonial evidence. Physical evidence is any object or item that establishes
a crime has been committed, such as blood, bite marks, hairs and many more. Testimonial
evidence is a statement or spoken words from a defendant, victim or witness. These can
take the form of eyewitness accounts and victim statements.
Collecting, Transferring and Storing Physical Evidence
One type of physical evidence is bodily fluids and tissues. Examples of bodily fluids collected
are: blood, semen and saliva. Blood can be tested at a crime scene, there are numerous
tests, one being the luminol test, where the chemical compound turns a luminent blue in the
presence of blood. Wet blood evidence is generally collected by crime scene investigators,
from blood pools but can also be collected off of clothing, using a gauze pad or a sterile
cotton cloth. Once the sample is collected it must be refrigerated or frozen and brought to a
laboratory. Dried blood can be found on small objects, the entire object can be sent to the
lab after its been properly packaged and labelled. However, when dried blood is found on a
larger object, an investigator should cover the stained area with paper and tape to avoid
contamination. Saliva is another bodily fluid, this can be visualised using the starch-iodine
test, which will result in a blue colour change when in contact with saliva. Saliva can be
found on a victim or offender, if bite marks were involved in the incident. To collect this, a
crime scene investigator will use a wet cotton swab, then place it in a vial for it to be
analysed by forensics. An example of a tissue is hair, if hair is found on clothing it should be
wrapped in paper or placed in a paper bag, sealed, labelled and sent for analysis, hair found
on furniture should be wrapped and labelled the same way. The processing of hair was
shown in the case of George Perot. In 1992 a single bit of hair was discovered by an FBI
agent on the bedsheet of a 78- year old woman who had been raped by a burglar in her
home in springfield. Peret was found near the crime scene at the time. Perot was put on trial,
despite the lack of physical evidence. Even the victim testified that the defendant looked
nothing like her attacker. He spent 30 years in jail due to hair comparison evidence. He was
later exonerated in a retrial in 2016, due to the fact FBI admitted it's hard to distinguish
individuals from a strand of hair and could not conclusively match with Perot’s.
Impression evidence is when a suspect presses something against a surface, an example of
this is bite marks. Crime scene investigators and police will corner off the crime scene to
preserve evidence they will also collect bitemark placement by giving suspects a styrofoam
to bite on leaving a patent. Both personnel must obtain a warrant under the under Police
and Criminal Evidence Act 1984 and then they can proceed to make a mold of the suspects
teeth as well as taking photos of the suspects mouth in various positions. All evidence will
then need to be placed into a bag and labelled. Evidence is then transported to a laboratory.
Forensic dentists then make a silicone cast of the bite mark. In the case of Ray Krone, he
was sentenced due to match of bite mark and teeth placement on the victim from the
suspect, it wasn't until 10 years later he was released due to DNA testing proving his
innocence. DNA testing conducted on the saliva and blood found on the victim excluded
Krone as the source and instead matched a man named Kenneth Phillips. Another type of
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