AC 1.3 Explain how evidence is processed
There are two types of evidence: physical evidence and testimonial evidence. Both of these
types of evidence can be used in criminal investigations to form a basis of argument for
either the prosecution or defence. It is one of the key elements of a case and can impact on
whether someone is guilty or not guilty. Physical evidence is anything that is tangible and
real, such as DNA, blood, fingerprints, weapons, etc. Testimonial evidence is anything that is
spoken, or a statement and these can be taken from witnesses, experts, the prosecution or
the defence.
Physical evidence
Physical evidence is an important part of cases as they are often always present on a crime
scene, and this is due to Locard’s exchange principle. This principle explains that there will
always be evidence on the crime scene and traces of evidence can be found on the victims,
offender, and vice versa. Every point of contact that is made will be able to be analysed by a
professional, most likely a SOCO or a forensic scientist, which will uncover certain detailed
evidence. Locard’s exchange principle was further developed by Paul Kirk who explained
that physical evidence is factual, and that it can prove one's innocence or guilt, and that it is
fundamentally down to human error if we are able to find the evidence and study it. A case in
which Locard's exchange principle was highlighted to be ineffective was the case of Barry
George. Barry George was wrongly imprisoned for the murder of Jill Dando on the basis that
he had a microscopic amount of gunpowder residue on his clothing that was linked to the
murder weapon. It was said that the gunpowder was likely from a police firearm touching his
clothing while they searched his flat, and this piece of evidence was enough for George to
be sent to prison, ultimately leading to a miscarriage of justice.
Personnel on the scene of a crime are concerned with arresting the offender, but also
collecting evidence and ensuring that it is uncontaminated so that it can be used in court as
admissible and reliable evidence. Police officers will be present at the crime scene first, and
must ensure that scene is protected and secure to ensure that it cannot be tampered with
and so ensure that the evidence is preserved in order for the SOCO’s to collect it. Scene of
crime officers will be at the crime scene to preserve and collect all of the physical evidence
which will then be sent securely to a lab for it to be further tested and analysed. Afterwards,
forensic scientists will be able to analyse the evidence in a lab.
When a crime scene is committed outdoors, it may be more difficult to preserve the crime
scene, and this is primarily due to the weather. It may be more difficult to preserve the
evidence if it is raining, snowing, foggy, etc, and this may cause evidence to not be found or
even destroyed. Furthermore, if the crime is outdoors in a public area, this may cause
interest from the general public, or even media outlets who want to report on the crime
scene, and this interest has the potential to contaminate any evidence. To prevent this from
happening, police must secure the crime scene, and they often do this with police tape, and
station police officers around the crime scene to ensure that the general public cannot go
inside of the covered area. When the SOCO’s are collecting the evidence, they need to be
wearing the appropriate protective bodysuits and using stools to ensure that they do not
contaminate the evidence.
