AC1.2 Assess the usefulness of
investigative techniques in criminal
investigations (20)
Forensics (Fingerprint analysis, DNA analysis)
Forensics is the application of scientific knowledge to legal problems, especially scientific
analysis of physical evidence. (This scientific knowledge is meant to be applied in court)
Examples:
• Fingerprints
• DNA
o Digital
o Blood splatter analysis
o Hair and fibre analysis
o Toxicology
o Ballistics
o Forensics entomology
Locards principle:
When two items come into contact, there is an exchange of microscopic material.
The perpetrator of a crime will bring something into the crime scene and leave something
with it.
It is the investigators duty to find these traces and reconstruct the events of the crime.
Fingerprints
2 features making fingerprints beneficial:
➢ Persistence – the principle that a persons fingerprints remain unchanged throughout
their lifetime
➢ Uniqueness – each persons fingerprint is unique and different to another persons
3 types of fingerprints:
Latent prints:
,Fingerprints are formed when the body’s natural oils and sweat which are on the skin
deposit onto another surface.
• Latent prints are not visible to the naked eye.
• Latent prints are found more easily on smooth non-porous surfaces
Collected by:
• Dusting a smooth surface with fingerprint powder (dusting)
• Alternate Light Source
• Chemical developers (porous surfaces)
• They then use adhesive tape or photography
Patent prints:
Fingerprints are formed when materials are transferred from the finger onto a surface.
o Patent prints are clearly visible to the naked eye
o Patent prints are usually made by substances such as, blood, dirt, ink or paint
Collected by:
o Patent prints are photographed in high resolution with a forensic measurement scale
in the image for reference
Plastic prints:
3D impression fingerprints which are made in a soft material such as wet paint, soap or wax.
Collected by:
o Photographs
o Caster moulds
Fingerprints: Classification & identification
Fingerprint class characteristics:
There are 3 fingerprint classes:
Arches – These are the least common,
about 5% of people have them
Whorls – These are common, about 30-35%
of people have them
,Loops – These are the most common, about 60-65% of people have them
Ridge characteristics:
o Tiny irregularities in the ridges (lines)
o These are unique to the individual
o Examples: core, hook, eye, bridgeway,
crossover
Fingerprint identification – the process of comparing fingerprints from humans to
determine whether these impressions could have come from the same individual
Classification & identification key facts:
• Both fingerprint class characteristics and ridge characteristics are used in
identification
• The process of matching ridge points is called ‘points of similarity’ or ‘points of
identification’
• In the UK, in order to identify someone with fingerprints you need to them to match
with 16 points
• A database contains the fingerprints of criminals (as well as DNA etc)
• Biometric scanners can now also be used
Evaluation
Advantages:
• You can see many people were at the crime scene.
• You can narrow down potential suspects (by seeing if they were at the crime scene)
• Persistence and uniqueness mean fingerprints are unique to one specific person and
they cannot be changed. This can reduce the risk of wrongful convictions as you will
only have fingerprints for specific people.
• Fingerprints are evidence that cannot be changed (objective)
• You can use fingerprints to help identify any weapons used, victims and witnesses
• You can use fingerprints to create a picture of what actually happened at the scene.
• Fingerprints reduce uncertainty of an identification
Disadvantages:
o You will need to have suspects already on the database to compare fingerprints etc
o If there are lots of background fingerprints, it could be hard to identify who was
involved in the crime and who was just passing by (possibly causing wrongful
convictions which can damage reputation)
o Fingerprints may be hard to extract, especially if they are outside etc. – They may
disappear from the weather.
o Time consuming – long process to collect, analyse and identify.
o Fingerprints can be easily cleaned off or prevented (for example by wearing gloves
you wont leave fingerprints, or you can wipe fingerprints off)
o Fingerprint analysis cannot be used for all crimes (some crimes don’t involve real
physical actions, such as technological crime or some non-utilitarian crimes)
, o You don’t know when fingerprints were left, meaning you cannot be fully sure if
they were there before, after or during the crime. (They are not time stamped)
o Fingerprints may only be partial prints and not full (this means it may be hard to find
16 prints and matches of something)
o Ethnic targeting may occur during fingerprint analysis
Fingerprint analysis is useful in property crimes, such as burglary where fingerprints are left
behind and can be analysed by forensics in the lab. For example, in a burglary fingerprint
analysis can be used to show the areas which the offender was in and how they got in and
out of the premises. However, you can only use fingerprint analysis on the items which they
took, but you may not have access to this as it would’ve already been taken.
Fingerprint analysis is not useful in crimes where no fingerprints were left behind and there
is no physical crime scene. Specifically technological crimes such as fraud and white collar
crime, this is because the crime is happening digitally/ remotely with no fingerprints being
left behind for the lab to analyse.
Case when fingerprint analysis helped catch the offender:
Robert Clarke
In 1984, when Robert Clarke was 16, he raped a woman in her home and forced her
flatmate to join in on the abuse. He escaped through the window and 25 years later he was
identified and found guilty due to the police finding his palm print on the window ledge.
Hew broke into the house and used an iron bar to force the woman and her flatmate to
undress. He tied them both up with cables and forced the flatmate to join in on the abuse.
He wore socks over his hands in attempt to avoid fingerprints being left. Scotland Yard
reopened the cold case and found a match between his palm print and the one left on the
window ledge.
However, the case of Shirley McKie shows mistaken fingerprint evidence.
DNA Analysis:
• DNA is deoxyribonucleic acid and consists of hereditary material.
• DNA is the coding of the parts of you that makes us unique
• DNA is unique to everyone (apart from identical twins)
• DNA determines our eye colour, hair colour and height etc.
DNA collection:
Sources of DNA:
• Hair cells
• Blood
• Skin cells
• Semen
investigative techniques in criminal
investigations (20)
Forensics (Fingerprint analysis, DNA analysis)
Forensics is the application of scientific knowledge to legal problems, especially scientific
analysis of physical evidence. (This scientific knowledge is meant to be applied in court)
Examples:
• Fingerprints
• DNA
o Digital
o Blood splatter analysis
o Hair and fibre analysis
o Toxicology
o Ballistics
o Forensics entomology
Locards principle:
When two items come into contact, there is an exchange of microscopic material.
The perpetrator of a crime will bring something into the crime scene and leave something
with it.
It is the investigators duty to find these traces and reconstruct the events of the crime.
Fingerprints
2 features making fingerprints beneficial:
➢ Persistence – the principle that a persons fingerprints remain unchanged throughout
their lifetime
➢ Uniqueness – each persons fingerprint is unique and different to another persons
3 types of fingerprints:
Latent prints:
,Fingerprints are formed when the body’s natural oils and sweat which are on the skin
deposit onto another surface.
• Latent prints are not visible to the naked eye.
• Latent prints are found more easily on smooth non-porous surfaces
Collected by:
• Dusting a smooth surface with fingerprint powder (dusting)
• Alternate Light Source
• Chemical developers (porous surfaces)
• They then use adhesive tape or photography
Patent prints:
Fingerprints are formed when materials are transferred from the finger onto a surface.
o Patent prints are clearly visible to the naked eye
o Patent prints are usually made by substances such as, blood, dirt, ink or paint
Collected by:
o Patent prints are photographed in high resolution with a forensic measurement scale
in the image for reference
Plastic prints:
3D impression fingerprints which are made in a soft material such as wet paint, soap or wax.
Collected by:
o Photographs
o Caster moulds
Fingerprints: Classification & identification
Fingerprint class characteristics:
There are 3 fingerprint classes:
Arches – These are the least common,
about 5% of people have them
Whorls – These are common, about 30-35%
of people have them
,Loops – These are the most common, about 60-65% of people have them
Ridge characteristics:
o Tiny irregularities in the ridges (lines)
o These are unique to the individual
o Examples: core, hook, eye, bridgeway,
crossover
Fingerprint identification – the process of comparing fingerprints from humans to
determine whether these impressions could have come from the same individual
Classification & identification key facts:
• Both fingerprint class characteristics and ridge characteristics are used in
identification
• The process of matching ridge points is called ‘points of similarity’ or ‘points of
identification’
• In the UK, in order to identify someone with fingerprints you need to them to match
with 16 points
• A database contains the fingerprints of criminals (as well as DNA etc)
• Biometric scanners can now also be used
Evaluation
Advantages:
• You can see many people were at the crime scene.
• You can narrow down potential suspects (by seeing if they were at the crime scene)
• Persistence and uniqueness mean fingerprints are unique to one specific person and
they cannot be changed. This can reduce the risk of wrongful convictions as you will
only have fingerprints for specific people.
• Fingerprints are evidence that cannot be changed (objective)
• You can use fingerprints to help identify any weapons used, victims and witnesses
• You can use fingerprints to create a picture of what actually happened at the scene.
• Fingerprints reduce uncertainty of an identification
Disadvantages:
o You will need to have suspects already on the database to compare fingerprints etc
o If there are lots of background fingerprints, it could be hard to identify who was
involved in the crime and who was just passing by (possibly causing wrongful
convictions which can damage reputation)
o Fingerprints may be hard to extract, especially if they are outside etc. – They may
disappear from the weather.
o Time consuming – long process to collect, analyse and identify.
o Fingerprints can be easily cleaned off or prevented (for example by wearing gloves
you wont leave fingerprints, or you can wipe fingerprints off)
o Fingerprint analysis cannot be used for all crimes (some crimes don’t involve real
physical actions, such as technological crime or some non-utilitarian crimes)
, o You don’t know when fingerprints were left, meaning you cannot be fully sure if
they were there before, after or during the crime. (They are not time stamped)
o Fingerprints may only be partial prints and not full (this means it may be hard to find
16 prints and matches of something)
o Ethnic targeting may occur during fingerprint analysis
Fingerprint analysis is useful in property crimes, such as burglary where fingerprints are left
behind and can be analysed by forensics in the lab. For example, in a burglary fingerprint
analysis can be used to show the areas which the offender was in and how they got in and
out of the premises. However, you can only use fingerprint analysis on the items which they
took, but you may not have access to this as it would’ve already been taken.
Fingerprint analysis is not useful in crimes where no fingerprints were left behind and there
is no physical crime scene. Specifically technological crimes such as fraud and white collar
crime, this is because the crime is happening digitally/ remotely with no fingerprints being
left behind for the lab to analyse.
Case when fingerprint analysis helped catch the offender:
Robert Clarke
In 1984, when Robert Clarke was 16, he raped a woman in her home and forced her
flatmate to join in on the abuse. He escaped through the window and 25 years later he was
identified and found guilty due to the police finding his palm print on the window ledge.
Hew broke into the house and used an iron bar to force the woman and her flatmate to
undress. He tied them both up with cables and forced the flatmate to join in on the abuse.
He wore socks over his hands in attempt to avoid fingerprints being left. Scotland Yard
reopened the cold case and found a match between his palm print and the one left on the
window ledge.
However, the case of Shirley McKie shows mistaken fingerprint evidence.
DNA Analysis:
• DNA is deoxyribonucleic acid and consists of hereditary material.
• DNA is the coding of the parts of you that makes us unique
• DNA is unique to everyone (apart from identical twins)
• DNA determines our eye colour, hair colour and height etc.
DNA collection:
Sources of DNA:
• Hair cells
• Blood
• Skin cells
• Semen
