Explain how evidence is processed
There are 2 types of evidence collected in criminal investigation: physical evidence and testimonial
evidence. Physical evidence is actual physical material such as DNA extracted from blood stains,
weapons, stolen goods recovered from the suspect. This type of evidence is tangible and is sent to a
forensic laboratory for processing. Testimonial evidence is written or oral statements by victims, eye
witnesses, expert witnesses and defendants.
Physical evidence is very important in an investigation because it’s present at almost every crime
scene. Locard’s exchange principle is the idea that every contact leaves a trace. This means that
material from the crime scene will be present on the offender or victim. Every time someone enters
a new environment they will leaves traces of DNA at the scene. You could argue that Locard’s
exchange principle can cause problems during a criminal investigation possibly leading to
miscarriages of justice. This was present in the Jill Dando case. Barry George was wrongly convicted
of her murder after the police found one ten thousandth of a centimetre of gunshot residue was
found in his jacket pocket which the police believed was from the gun that was used to murder Jill
Dando. The gunshot residue was actually from the police firearms that were taken into his flat whilst
being searched. The reside then ended up inside his pocket. This resulted in a miscarriage of justice
.
Hair
At a crime scene hair is collected by the CSI. Before they move the hair strands they take a
photograph of the hair on the object it was found on. Hair fibres can be collected using clean
tweezers, tape lifted or vacuumed using a filter if the hairs are not visible. If they are extracting hairs
from a person the CSI collect a sample of 25 plucked hairs from their bodily region. Once the hair
fibres are collected they are wrapped and placed in a paper bag. The paper bag is he sealed in an
evidence bag and secured in a locked vehicle to be transported to the laboratory. Forensic scientists
analyse the hair fibres under a microscope. Animal hairs found on items of evidence can link a
suspect to a crime scene, a vehicle and give the police a location where the victim was held. Hair can
be used to identify a victim or a suspect. They can do this by extracting DNA from cells in the root.
Hairs can also help distinguish a victim or offenders’ race and tell the investigators which part of the
body the hairs are from. Forensic scientists can also do toxicology tests. This tests to see whether the
victim or offender consumed alcohol or drugs at the time of the offence. This is because alcohol and
drugs are secreted in the hair as it grows. This test was used in the case of Shannon Mathews.
Shannon was kidnaped by her uncle in a plot with her mother to receive the £50,000 reward for
finding her. She was found 24 days later hidden in a storage drawer under the bed. A toxicology test
on hair samples from Shannon found that she had regular doses of the potent hypnotic drug
temazepam in the months before she vanished. Traces of the drug were found in each segment of
her hair showing they were ingested over an extended period (for the past 20 months).
Blood
At a crime scene blood is collected by the CSI. The CSI can analyse blood splatter at the scene, to see
if there are any trials from the scene or pools of blood. Items with dry blood on them should be
carefully packaged in a sealed container and labelled. Fabric with wet blood on them should be
allowed to air dry and this should not be folded so blood doesn’t transfer and get contaminated.
Liquid form blood stains are collected in a sterile material and then left at room temperature to dry.
The blood is carefully packaged and sent as soon as possible (within 24 hours) to the forensic
laboratory for analysis. Blood can be stored for many years meaning it’s very useful in cold cases.
Blood can eliminate a suspect or provide evidence against them. Forensics scientists can use
toxicology and evaluate someone’s DNA to look for their ID, find their blood type and look for things
in their system such as alcohol or drugs. In the Steven Lawrence case a microscopic amount of blood
There are 2 types of evidence collected in criminal investigation: physical evidence and testimonial
evidence. Physical evidence is actual physical material such as DNA extracted from blood stains,
weapons, stolen goods recovered from the suspect. This type of evidence is tangible and is sent to a
forensic laboratory for processing. Testimonial evidence is written or oral statements by victims, eye
witnesses, expert witnesses and defendants.
Physical evidence is very important in an investigation because it’s present at almost every crime
scene. Locard’s exchange principle is the idea that every contact leaves a trace. This means that
material from the crime scene will be present on the offender or victim. Every time someone enters
a new environment they will leaves traces of DNA at the scene. You could argue that Locard’s
exchange principle can cause problems during a criminal investigation possibly leading to
miscarriages of justice. This was present in the Jill Dando case. Barry George was wrongly convicted
of her murder after the police found one ten thousandth of a centimetre of gunshot residue was
found in his jacket pocket which the police believed was from the gun that was used to murder Jill
Dando. The gunshot residue was actually from the police firearms that were taken into his flat whilst
being searched. The reside then ended up inside his pocket. This resulted in a miscarriage of justice
.
Hair
At a crime scene hair is collected by the CSI. Before they move the hair strands they take a
photograph of the hair on the object it was found on. Hair fibres can be collected using clean
tweezers, tape lifted or vacuumed using a filter if the hairs are not visible. If they are extracting hairs
from a person the CSI collect a sample of 25 plucked hairs from their bodily region. Once the hair
fibres are collected they are wrapped and placed in a paper bag. The paper bag is he sealed in an
evidence bag and secured in a locked vehicle to be transported to the laboratory. Forensic scientists
analyse the hair fibres under a microscope. Animal hairs found on items of evidence can link a
suspect to a crime scene, a vehicle and give the police a location where the victim was held. Hair can
be used to identify a victim or a suspect. They can do this by extracting DNA from cells in the root.
Hairs can also help distinguish a victim or offenders’ race and tell the investigators which part of the
body the hairs are from. Forensic scientists can also do toxicology tests. This tests to see whether the
victim or offender consumed alcohol or drugs at the time of the offence. This is because alcohol and
drugs are secreted in the hair as it grows. This test was used in the case of Shannon Mathews.
Shannon was kidnaped by her uncle in a plot with her mother to receive the £50,000 reward for
finding her. She was found 24 days later hidden in a storage drawer under the bed. A toxicology test
on hair samples from Shannon found that she had regular doses of the potent hypnotic drug
temazepam in the months before she vanished. Traces of the drug were found in each segment of
her hair showing they were ingested over an extended period (for the past 20 months).
Blood
At a crime scene blood is collected by the CSI. The CSI can analyse blood splatter at the scene, to see
if there are any trials from the scene or pools of blood. Items with dry blood on them should be
carefully packaged in a sealed container and labelled. Fabric with wet blood on them should be
allowed to air dry and this should not be folded so blood doesn’t transfer and get contaminated.
Liquid form blood stains are collected in a sterile material and then left at room temperature to dry.
The blood is carefully packaged and sent as soon as possible (within 24 hours) to the forensic
laboratory for analysis. Blood can be stored for many years meaning it’s very useful in cold cases.
Blood can eliminate a suspect or provide evidence against them. Forensics scientists can use
toxicology and evaluate someone’s DNA to look for their ID, find their blood type and look for things
in their system such as alcohol or drugs. In the Steven Lawrence case a microscopic amount of blood
