AC 1.3: Explain How Evidence is Processed
Evidence can be categorised into two categories: physical evidence, such as bodily fluids and tissues,
and testimonial evidence, which is classified as written or spoken evidence from people such as
witnesses or suspects.
Locard’s principle can be applied to physical evidence, which states that every time someone enters
an environment, such as a crime scene, something is added and removed – ‘every contact leaves a
trace’. Physical evidence includes bodily fluids/tissues, (blood, semen, saliva, fingerprints, etc.),
impression evidence, (shoe prints, etc.) and trace evidence, (glass fragments, clothing fibres, etc.).
All physical evidence must first be photographed before it is collected. Bodily fluids and tissues must
be allowed to dry first before they are collected to prevent transference. They are then carefully
packaged and sent for analysis, ideally within 24 hours. They may be carefully packaged by being
sealed in a paper bag within a polythene bag, such as is the method with semen. Individual items
such as hairs or skin flakes must be collected, bagged, labelled and sent for analysis in the same
manner. Fingerprints are dusted with magnesium powder or a UV light is shone onto them. After
photographing, moulds may be made or prints may be preserved, such as being lifted with acetate.
Impression evidence may have casts made, such as for shoeprints or teeth marks. Trace evidence
may help place a suspect at the scene by comparing soil, fibres or paint with traces that were found
on their person, or may help determine the time of death based on how developed the larvae of
blowflies are.
Many cases have been affected by the mishandling or mis-collection of physical evidence, such as
Barry George, who was sentenced to life for the murder of TV presenter Jill Dando in 1999. This was
due to gunshot residue measuring 1/1000 of a cm being found in his jacket pocket, but this residue
was later confirmed to be from the police’s firearms that they used whilst searching his flat for
evidence. As a result, in 2008 he was acquitted after spending 7 years in prison. Similarly, Amanda
Knox was also falsely imprisoned due to the mis-collection of physical evidence: she was sentenced
to 26 years in prison for the murder of Meredith Kercher, because both their DNA was found on the
suspected murder weapon. However, Kercher’s DNA was later said to be present due to
contamination, as proper DNA procedures weren’t followed. After all, Kercher’s bra clasp was
collected from the floor so long after her death that contamination was highly likely.
The second type of evidence is testimonial evidence, which consists of written or spoken evidence
from witnesses, suspects and victims. Statements must be admissible in court, meaning they would
not be considered in reaching a verdict. Statements from eyewitnesses, victims and experts are
usually taken from both the defence and prosecution and are disclosed prior to court. Evidence may
be agreed as being true by both sides, and therefore read out in court, rather than the witness giving
evidence in the witness box. Vulnerable witnesses, however, may choose to give evidence by video
link. Defendants cannot be forced to give evidence, and may refuse to enter the witness box. Some
evidence may be consider3ed inadmissible in court, including hearsay or rumoured evidence, i.e.,
repeating a rumour they heard rather than describing what they saw, a forced confession, i.e.
violence or threats have been used to extract a confession from the defendant, or entrapment such
as honeytraps, i.e. the police have tried to trick the defendant into confessing or committing to a
crime.
A number of cases have also been affected by inadmissible or incorrect testimonial evidence being
shared in court. An example of this is Sally Clark, who was given two life sentences for the murder of
her two infant children in 1999. A key piece of evidence used to decide this verdict came from
Professor Sir Roy Meadow’s testimony, in which he stated that the likelihood of both deaths being
accidental was around “1 in 73 million”. However, this was found to be grossly inaccurate. As a
