AC1.3:
Evidence is central to the process of investigating and prosecuting in a case, it is the basis in
which a suspect can be charged, tried and found guilty or innocent. The process of collecting
and storing evidence must be done with care to ensure it's not damaged or contaminated to
provide the case with reliable evidence. There are two types of evidence, physical evidence,
being actual material, and testimonial evidence, written or oral statements given by victimes,
eye witnesses, expert witnesses and defendants.
Physical evidence is an extremely important part of investigations, and to ensure it is ruled as
admissible in court, collecting, transferring, storing and analysing must be done with an intense
amount of care, since as stated by Locard’s exchange principle, “every contact leaves a trace”.
Because of how easily evidence can be contaminated, when processing a crime scene, SOCOs
gathering evidence must wear the correct type of clothing, being a full protective suit, shoes and
gloves. There are many different types of physical evidence, for example, bodily fluids, such as
blood, semen and saliva, and tissues, such as skin flakes and hair can be vital in the
identification of people involved in an investigation. DNA can be extracted from bodily fluids and
tissues and compared with control samples from suspects to identify a match. When blood can
be used as evidence, it should be able to air dry, and carefully packaged and sent for analysis
within 24 hours to a forensics laboratory. Wet blood on fabric should not be folded as it will
transfer to other parts of an item . Saliva can be used as evidence from things such as bites
inflicted on a victim, which can be collected by taking swabs to provide a sample for DNA
analysis. Semen can be found on bedding or clothing, and like blood, should be allowed to air
dry before packaged in a paper bag, sealed and placed in a polythene bag, which is then sealed
and labelled. Items should be packaged and stored separately, and where there has been a
sexual assault victim, they should be examined as soon as possible by either a police surgeon
or a doctor for swabs to be taken and analysed. Skin flakes constantly shed in small quantities,
and can also be analysed for DNA, as well as hairs which can be matched to a suspect. If hairs
are found, then they should be wrapped in paper or placed in a paper bag, sealed, labelled and
transferred to a forensics lab for analysis.
Another form of physical evidence is fingerprints, which are unique to every individual, providing
for valuable identification evidence. Prints are skin ridges which leave marks or impressions
from sweat or contaminants, in or on surfaces. There are 3 types of fingerprints, latent prints,
which are invisible marks left on a surface that can be made visible for collection by dusting with
magnesium powder or shining a UV light. They are then collected by using an adhesive strip
which is placed on an acetate sheet. The second type of print is patent prints, visible to the
naked eye which may be left in thick, liquid substances such as blood. The third print is plastic
prints, which are 3D shapes made by pressing fingers into soft material such as putty on a
window frame. Prints should be photographed, and if possible a mould should be made from
them in order to capture impressions. Live Scan scanners and lantern portable units can also be
used to scan and match fingerprints.
Evidence is central to the process of investigating and prosecuting in a case, it is the basis in
which a suspect can be charged, tried and found guilty or innocent. The process of collecting
and storing evidence must be done with care to ensure it's not damaged or contaminated to
provide the case with reliable evidence. There are two types of evidence, physical evidence,
being actual material, and testimonial evidence, written or oral statements given by victimes,
eye witnesses, expert witnesses and defendants.
Physical evidence is an extremely important part of investigations, and to ensure it is ruled as
admissible in court, collecting, transferring, storing and analysing must be done with an intense
amount of care, since as stated by Locard’s exchange principle, “every contact leaves a trace”.
Because of how easily evidence can be contaminated, when processing a crime scene, SOCOs
gathering evidence must wear the correct type of clothing, being a full protective suit, shoes and
gloves. There are many different types of physical evidence, for example, bodily fluids, such as
blood, semen and saliva, and tissues, such as skin flakes and hair can be vital in the
identification of people involved in an investigation. DNA can be extracted from bodily fluids and
tissues and compared with control samples from suspects to identify a match. When blood can
be used as evidence, it should be able to air dry, and carefully packaged and sent for analysis
within 24 hours to a forensics laboratory. Wet blood on fabric should not be folded as it will
transfer to other parts of an item . Saliva can be used as evidence from things such as bites
inflicted on a victim, which can be collected by taking swabs to provide a sample for DNA
analysis. Semen can be found on bedding or clothing, and like blood, should be allowed to air
dry before packaged in a paper bag, sealed and placed in a polythene bag, which is then sealed
and labelled. Items should be packaged and stored separately, and where there has been a
sexual assault victim, they should be examined as soon as possible by either a police surgeon
or a doctor for swabs to be taken and analysed. Skin flakes constantly shed in small quantities,
and can also be analysed for DNA, as well as hairs which can be matched to a suspect. If hairs
are found, then they should be wrapped in paper or placed in a paper bag, sealed, labelled and
transferred to a forensics lab for analysis.
Another form of physical evidence is fingerprints, which are unique to every individual, providing
for valuable identification evidence. Prints are skin ridges which leave marks or impressions
from sweat or contaminants, in or on surfaces. There are 3 types of fingerprints, latent prints,
which are invisible marks left on a surface that can be made visible for collection by dusting with
magnesium powder or shining a UV light. They are then collected by using an adhesive strip
which is placed on an acetate sheet. The second type of print is patent prints, visible to the
naked eye which may be left in thick, liquid substances such as blood. The third print is plastic
prints, which are 3D shapes made by pressing fingers into soft material such as putty on a
window frame. Prints should be photographed, and if possible a mould should be made from
them in order to capture impressions. Live Scan scanners and lantern portable units can also be
used to scan and match fingerprints.
