A.C. 1.3 – Explain how evidence is processed
There are two types of evidence collected in criminal investigations: physical evidence and testimonial evidence.
Physical evidence is real and consists of tangible articles, such as blood, DNA, Hair, footprints, or a weapon. On the
other and testimonial evidence is a statement or spoken words from a defendant, victim, or witness. These can take
the form of eyewitness accounts of victim’s statements.
Physical evidence being present in almost every criminal case, this could be due to Locard’s Exchange Principle,
which states that every contact leaves a trace, this means that material from the crime scene (including that of the
victim) will be present on the offender. Trace evidence – is when objects make contact, leaving behind physical
evidence that can be analyzed and collected such as hair samples left on carpet in a crime scene, hair can be
matched to a suspect, 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. A case example
is ‘George Perrot’. He spent almost 30 years in prison thanks to a single hair. It was discovered by an FBI agent on the
bedsheet of a 78-year-old woman who had been raped. despite the absence of physical evidence tying him to the
crime scene. There was no semen. There was no blood. And so, there was no way to conduct a conclusive DNA test.
Even the victim testified that the defendant looked nothing like her attacker: he had a short haircut and was clean-
shaven, while Perrot had a long shaggy mop, a moustache, and a goatee beard. However, exchange of physical
evidence can cause issues during criminal cases, as seen in the case of Barry George, where gunshot residue of one
ten thousand of a centi-metre was found in his jacket. This led to Barry George being wrongfully convicted of
murder. The gunshot residue was said to have come from the police firearms that were taken to his flat, and so it
ended on his jacket, leading to miscarriage of justice.
Impression evidence such as bite marks, will be collect a sample bite mark from the suspect, an SOCO and Police will
corner off the crime scene to preserve evidence they will also collect bitemark placement by giving suspect a
Styrofoam to bite on leaving a patent, both personnel must obtain a warrant under Police and Criminal evidence Act
1984 and then they can proceed to make a mold of the suspect's teeth as well as take photos of the suspect's mouth
in various positions. Storage and transfer of bite marks will depend if victim is alive or deceased, if on deceased
victims, they evidence is cut out from the skin in the morgue and preserved in a compound called formalin, which
contains formaldehyde. All evidence will need to be placed into a bag which is tamper proof, all evidence has to be
labelled which is a requirement under the Criminal Justice Act 1967, the label need to contain 4 details. 1. Name of
CSI who recovered it, 2. Date it was recovered. 3. Location it was recovered from. 4. Identifying mark e.g. 12345 (CSI
job nom.) ELF (CSI initial) 5 (sample nom.) so the mark identifying mark will be 12345ELF5. Evidence is then
transported in a vehicle, that has been selected in a specific method, due to each physical evidence having different
factors that need to be considered such as heat, rain, magnetic field in case of USB or device evidence. Forensic
dentists then make a silicone cast of the bite mark. Analysis of evidence need to follow a protocol, first identify it as
human, bite is swabbed for DNA, which may have been left in the saliva of the biter, take measurements of each
individual bite mark, and record it. such as bite marks on deceased victims and Odonatologist will analyse it in a
forensic laboratory. A Case of ‘Ray Krone’ were he was sentenced due to a 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.
When dealing with an outdoor crime scene, physical evidence can become problematic, for example weather
condition such as rain, as it is containing sulphuric acid, meaning it is acidic can destroy and contaminate evidence.
Rendering it useless in a criminal investigation, in addition to this, the evidence may simple be lost or destroyed by
harsh weather condition such as wind or snow, outdoor crime scenes often attract media which could impact the
reliability of the evidence due to contamination, and these factors should be considered when testing the evidence
found. To mitigate against these potential issues, it is vital for the police to secure the crime scene by putting up
temporary structures such as tents, and ensure the scene is not contaminated by wearing bodysuits and using
stepping stools when collecting evidence. Due to the public nature of the crime scene, police cant be sure that
evidence found at the crime scene from the offender, Is not contaminated or tampered with, this hinders its
reliability for CPS as they might not have the crucial evidence needed to secure a conviction for the offender.
Because as Locard’s exchange principle claims material from the crime scene including victims ill be present on the
offender or it will be transported due to objects or people coming in contact with it as seen in the Barry George case.
