Unit 3 AC1.3 Explain how evidence is processed
Evidence is the bases on which a suspect is charged, tried and found either guilty or not
guilty, and can either be physical or testimonial.
Physical evidence
Physical evidence is any tangible, physical material that can establish that a crime has been
committed or can link a crime and its victim/perpetrator, for example DNA, stolen goods,
footprints and weapons. Physical evidence is a key part of criminal investigations as it is
presented in almost every case, so it is necessary that it is handled with great care so it is
uncontaminated and can be used in court. It is so important as a result of Locard’s exchange
principle, of ‘every contact leaves a trace’, meaning that every time someone enters an
environment, something is added to and removed from it (which applies to contact between
individuals as well as between individuals and the physical environment. Paul Kirk described
that “Wherever the offender steps, whatever he touches, whatever he leaves, even
unconsciously, will serve as a silent witness against him.” Therefore, professionals assume
there will definitely be some physical evidence left at the scene and it’s their job to find it.
Scene of crime officers (SOCO’s) arrive after police officers have secured, protected and
preserved evidence at a crime scene. They have to then collect this evidence and transfer it
to a laboratory to be analysed, without it being contaminated (which could happen through
handling items without gloves, or by breathing, sneezing or coughing over them). To prevent
this SOCO’S usually wear protective clothing (especially for more serious crimes) to protect
themselves and avoid contamination. Outdoor crime scenes are particularly problematic due
to harsh weather conditions, as evidence may be lost/destroyed, and media interest, which
could impact the reliability of the evidence due to contamination. To stop these police may
secure the crime scene by putting up temporary structures and wearing bodysuits and using
stepping stools when collecting evidence to avoid contamination.
Body fluids and tissues provide important identification (DNA) evidence that can be used in
investigations so must be collected in certain ways. Blood should be allowed to dry at room
temperature, with fabric bearing wet blood to remain unfolded (stopping it from transferring
to other areas of the item), and it should then be packaged individually in evidence bags and
sent within 24 hours to a forensics laboratory for analysis. Semen should be allowed to air
dry on the original item, and then placed in a paper bag individually which should be sealed,
and then in a plastic evidence bag that is sealed and labelled and sent to forensics for
analysis. If a person has been sexually assaulted, they should be taken to a doctor for
swabs to be taken. Saliva should be swabbed and packaged carefully in an evidence bag, to
provide a sample for DNA analysis. Skin flakes may be found at the crime scene, and can be
analysed for DNA. Hairs should be picked up from the victim/suspect using tweezers and
bagged. Fabric with hairs or furniture with hairs on should be put in paper bags, sealed,
labelled and sent for analysis. DNA can also be extracted from hair root cells and can also
indicate the race of the person they came from, as well as the body part the hair is from.
Fingerprints are valuable identification evidence as they are unique to each individual (even
identical twins have different prints, so they’re more useful than DNA). Fingerprints are made
up of patterns of tiny ridges on the skin and a lot of time and effort is put into finding and
preserving them. Unique palm, toe and foot sole prints can also be found. So that searches
can be done to see if there’s a match of this unique evidence, it is logged into databases like
INDENTI. There are 3 types are fingerprints: Latent, Patent and Plastic prints.
Latent prints are invisible to the naked eye, and are a result of natural oils in the skin. They
can be made visible using magnesium powder, containing an adhesive chemical that is
Evidence is the bases on which a suspect is charged, tried and found either guilty or not
guilty, and can either be physical or testimonial.
Physical evidence
Physical evidence is any tangible, physical material that can establish that a crime has been
committed or can link a crime and its victim/perpetrator, for example DNA, stolen goods,
footprints and weapons. Physical evidence is a key part of criminal investigations as it is
presented in almost every case, so it is necessary that it is handled with great care so it is
uncontaminated and can be used in court. It is so important as a result of Locard’s exchange
principle, of ‘every contact leaves a trace’, meaning that every time someone enters an
environment, something is added to and removed from it (which applies to contact between
individuals as well as between individuals and the physical environment. Paul Kirk described
that “Wherever the offender steps, whatever he touches, whatever he leaves, even
unconsciously, will serve as a silent witness against him.” Therefore, professionals assume
there will definitely be some physical evidence left at the scene and it’s their job to find it.
Scene of crime officers (SOCO’s) arrive after police officers have secured, protected and
preserved evidence at a crime scene. They have to then collect this evidence and transfer it
to a laboratory to be analysed, without it being contaminated (which could happen through
handling items without gloves, or by breathing, sneezing or coughing over them). To prevent
this SOCO’S usually wear protective clothing (especially for more serious crimes) to protect
themselves and avoid contamination. Outdoor crime scenes are particularly problematic due
to harsh weather conditions, as evidence may be lost/destroyed, and media interest, which
could impact the reliability of the evidence due to contamination. To stop these police may
secure the crime scene by putting up temporary structures and wearing bodysuits and using
stepping stools when collecting evidence to avoid contamination.
Body fluids and tissues provide important identification (DNA) evidence that can be used in
investigations so must be collected in certain ways. Blood should be allowed to dry at room
temperature, with fabric bearing wet blood to remain unfolded (stopping it from transferring
to other areas of the item), and it should then be packaged individually in evidence bags and
sent within 24 hours to a forensics laboratory for analysis. Semen should be allowed to air
dry on the original item, and then placed in a paper bag individually which should be sealed,
and then in a plastic evidence bag that is sealed and labelled and sent to forensics for
analysis. If a person has been sexually assaulted, they should be taken to a doctor for
swabs to be taken. Saliva should be swabbed and packaged carefully in an evidence bag, to
provide a sample for DNA analysis. Skin flakes may be found at the crime scene, and can be
analysed for DNA. Hairs should be picked up from the victim/suspect using tweezers and
bagged. Fabric with hairs or furniture with hairs on should be put in paper bags, sealed,
labelled and sent for analysis. DNA can also be extracted from hair root cells and can also
indicate the race of the person they came from, as well as the body part the hair is from.
Fingerprints are valuable identification evidence as they are unique to each individual (even
identical twins have different prints, so they’re more useful than DNA). Fingerprints are made
up of patterns of tiny ridges on the skin and a lot of time and effort is put into finding and
preserving them. Unique palm, toe and foot sole prints can also be found. So that searches
can be done to see if there’s a match of this unique evidence, it is logged into databases like
INDENTI. There are 3 types are fingerprints: Latent, Patent and Plastic prints.
Latent prints are invisible to the naked eye, and are a result of natural oils in the skin. They
can be made visible using magnesium powder, containing an adhesive chemical that is
