AC1.3
Explain how evidence is processed
Physical Evidence:
• Physical evidence is the materials which you can take away from the crime scene (for
example, weapons, fingerprints, fibres, impressions)
Physical evidence follows the principle of Locards Principle: When two items come into
contact, there is an exchange of microscopic material, this means that the perpetrator will
bring something into the crime scene and leave something with it.
• The stages of processing physical evidence are: Collection, Analysis, Transfer, Storage
and personnel.
Collection:
There are 6 stages of processing a crime scene:
1. Identify hazards
2. Protect the scene
3. Walk through
4. Document the scene
5. Search
6. Collect evidence
The crime should always be protected to ensure that there is no contamination with the
physical evidence. The most common cause of contamination with evidence is often from
not wearing gloves while handling evidence. In order to prevent contamination,
investigators use tape, protective clothing, tents, stepping stones and police officers (to
guard the scene).
Analysis/ Collection:
During an investigation, investigators must document the scene. In order to do this, they
must, ensure nothing is touched or moved, photographing the scene, placing evidence
markers next to key areas, sketching scenes to identify distances, and writing notes to
document thoughts and suspicions about evidence.
During an investigation, investigators must search the scene. They may do this through
techniques such as grid search pattern, zone search, outward spiral. - This must be done in a
methodical way.
Different types of physical evidence are collected differently:
Hair And Fibre:
, • Hair and fibres can easily be disturbed, so in order to collect you must wear
protective suits to avoid contamination and use tapings and tweezers. During
analysis, they use a microscope to identify the type. Hairs can be used to show DNA
which can find where fibres are from, identify race and if the hair was dyed. They can
then use a toxicology test to show if drugs have been used. - This is shown in Shannon
Matthews
Footprint Analysis:
• In order to collect footprints, we can use ESLA machines to lift up dust particles to
then reveal prints. We can then use casting powder and water to take casts. While
analysing footprints, we look for identifying features such as the size and possible
signs of wear. Footprint identification technology can then be used to identify who
the footprint belonged to.
Fingerprints:
• To collect fingerprints, we use high intensity lights to reveal and take photos of the
prints. We can use dustings (such as aluminium powder) to reveal prints. We can lift
prints using tape, or we may use superglue to vaporise prints. When analysing, we
can use computer databases to identify who the fingerprints belong to and look for
unique characteristics. The three types of fingerprints are latent, patent and plastic.
Ballistics:
• When collecting ballistics, we look for projectiles and weapons. We can then use
rods to locate bullets and find where the shot was fired from, this can also help
identify what gun was used. We can use a bullet retrieval tank to preserve bullets.
We can then analyse using a microscope and enter into a computer system to
identify it the gun has been used in other crimes.
Biological evidence:
• Biological evidence includes blood and semen. We can use gloves, swab boxes and
swabs (by swirling to collect DNA) to collect. When analysing, we then seal the swab
to avoid contamination so it can then be analysed.
Case – contamination during collection - Meredith Kercher:
Amanda Knox was wrongly convicted of the murder of Meredith Kercher after her DNA was
supposedly at the scene. However, the evidence (the bra and the knife) went under
retesting and the police found contamination of the evidence. And, that there was actually
no DNA on the evidence which was originally the reason for the arrest of Amanda Knox. -
This case shows that proper DNA procedures were not followed. - These findings led to
Amanda Knox being released due to ‘lack of biological traces’
Transfer & Storage
When storing physical evidence we must use the chain of custody.
Explain how evidence is processed
Physical Evidence:
• Physical evidence is the materials which you can take away from the crime scene (for
example, weapons, fingerprints, fibres, impressions)
Physical evidence follows the principle of Locards Principle: When two items come into
contact, there is an exchange of microscopic material, this means that the perpetrator will
bring something into the crime scene and leave something with it.
• The stages of processing physical evidence are: Collection, Analysis, Transfer, Storage
and personnel.
Collection:
There are 6 stages of processing a crime scene:
1. Identify hazards
2. Protect the scene
3. Walk through
4. Document the scene
5. Search
6. Collect evidence
The crime should always be protected to ensure that there is no contamination with the
physical evidence. The most common cause of contamination with evidence is often from
not wearing gloves while handling evidence. In order to prevent contamination,
investigators use tape, protective clothing, tents, stepping stones and police officers (to
guard the scene).
Analysis/ Collection:
During an investigation, investigators must document the scene. In order to do this, they
must, ensure nothing is touched or moved, photographing the scene, placing evidence
markers next to key areas, sketching scenes to identify distances, and writing notes to
document thoughts and suspicions about evidence.
During an investigation, investigators must search the scene. They may do this through
techniques such as grid search pattern, zone search, outward spiral. - This must be done in a
methodical way.
Different types of physical evidence are collected differently:
Hair And Fibre:
, • Hair and fibres can easily be disturbed, so in order to collect you must wear
protective suits to avoid contamination and use tapings and tweezers. During
analysis, they use a microscope to identify the type. Hairs can be used to show DNA
which can find where fibres are from, identify race and if the hair was dyed. They can
then use a toxicology test to show if drugs have been used. - This is shown in Shannon
Matthews
Footprint Analysis:
• In order to collect footprints, we can use ESLA machines to lift up dust particles to
then reveal prints. We can then use casting powder and water to take casts. While
analysing footprints, we look for identifying features such as the size and possible
signs of wear. Footprint identification technology can then be used to identify who
the footprint belonged to.
Fingerprints:
• To collect fingerprints, we use high intensity lights to reveal and take photos of the
prints. We can use dustings (such as aluminium powder) to reveal prints. We can lift
prints using tape, or we may use superglue to vaporise prints. When analysing, we
can use computer databases to identify who the fingerprints belong to and look for
unique characteristics. The three types of fingerprints are latent, patent and plastic.
Ballistics:
• When collecting ballistics, we look for projectiles and weapons. We can then use
rods to locate bullets and find where the shot was fired from, this can also help
identify what gun was used. We can use a bullet retrieval tank to preserve bullets.
We can then analyse using a microscope and enter into a computer system to
identify it the gun has been used in other crimes.
Biological evidence:
• Biological evidence includes blood and semen. We can use gloves, swab boxes and
swabs (by swirling to collect DNA) to collect. When analysing, we then seal the swab
to avoid contamination so it can then be analysed.
Case – contamination during collection - Meredith Kercher:
Amanda Knox was wrongly convicted of the murder of Meredith Kercher after her DNA was
supposedly at the scene. However, the evidence (the bra and the knife) went under
retesting and the police found contamination of the evidence. And, that there was actually
no DNA on the evidence which was originally the reason for the arrest of Amanda Knox. -
This case shows that proper DNA procedures were not followed. - These findings led to
Amanda Knox being released due to ‘lack of biological traces’
Transfer & Storage
When storing physical evidence we must use the chain of custody.
