There are two different types of evidence; physical evidence and testimonial evidence. Dr
Edmond Locard formulated the principle of exchange, which means anyone who enters a
scene both takes something of the scene away with them and leaves something of
themselves behind. Every contact leaves a trace, such as fingerprints, DNA, fibres or
footwear marks- this is known as physical evidence. Physical evidence can be both patent
(can be physically seen e.g. visible fingerprints in blood) or latent (not initially visible). On the
other hand, testimonial evidence is the spoken word of witnesses, which can include both
the victim and defendant. All evidence must be admissible, which means it complies with the
rules of evidence.
Physical evidence must be photographed before collection from the SOCO. Blood stains and
semen stains can be collected on sterile material and if still a liquid, should be left to dry on
the material at room temperature before they are collected in order to reduce transference.
They are then packaged (all exhibits packaged separately) and need to be transferred to a
forensic lab, preferably within 24 hours. Blood stains are stored in a labelled, sealed
container and semen stains must be carefully wrapped in paper, sealed in a polythene bag.
These are then analysed in a forensic lab for blood type and DNA markers in order to create
a DNA profile. Any individual items such as hair samples and fibres and threads are handled
in a similar but slightly different manner. Hair samples can be collected on clothing which can
be wrapped in paper, or a small tool can be used to pick up the hair and fibres & threads are
often found on their items or caught in torn materials. These must be picked up with gloved
fingers or tweezers and then sent to a forensic lab for investigation. Small fragments of hair
should be placed in paper which is marked and sealed and fibres should be wrapped in an
envelope also sealed and marked. These can be analysed under a microscope and they
undergo toxicology exams for multiple pieces of evidence. Hair samples can reveal both the
race of the individual and where the hair itself came from, and fibres and threads can reveal
the type or colour of the fabric they come from and comparisons can be made to the
suspects clothes. A case example of where hair and fibres were used was in the case of
Sarah Payne. Sarah’s hair and fibres from her jumper were found in Roy Whiting’s van.
There were also fibres on her shoe that matched the passenger seat cover in the van and
her hair was found on the sweater. Roy Whiting was found guilty of the murder. With
fingerprints, if patent and left in liquid such as blood, photographs are taken for a lasting
record. If impressed into a soft material or tissue they can be photographed or put into a
mould if they are fragile. They are stored as photographs or a mould and are put into a
database to help future cases. It also has to be ensured that they are stored in a cool, dry
place. For analysis, fingerprints are dusted with a powder or chemical agent, such as
magnesium powder or a UV light is shone in order to reveal the unique imprints. Impression
casts can be made for shoe prints or bite marks. Bite marks are transferred to a forensic
odontologist whilst show prints are transferred to a regular forensic laboratory. Bite marks
can be marked back ton the suspect, and are common in sexual assault cases. Shoe prints
can let police know what type of shoes to look for when searching a suspect's home and can
also show weight, patterns of walking and where the suspect or victim has been. When
collecting any physical evidence, it is extremely important that the SOCO’s or CSI’s will wear
a bodysuit and gloves to ensure that the evidence is not contaminated by their own clothes
or hair. Contamination of physical evidence has caused wrongful convictions in the past, for
example in the case of Barry George. Barry was found guilty of the death of Jill Dando, shot
outside of her home on 26 april 1999 and he was arrested and charged for her murder in
Edmond Locard formulated the principle of exchange, which means anyone who enters a
scene both takes something of the scene away with them and leaves something of
themselves behind. Every contact leaves a trace, such as fingerprints, DNA, fibres or
footwear marks- this is known as physical evidence. Physical evidence can be both patent
(can be physically seen e.g. visible fingerprints in blood) or latent (not initially visible). On the
other hand, testimonial evidence is the spoken word of witnesses, which can include both
the victim and defendant. All evidence must be admissible, which means it complies with the
rules of evidence.
Physical evidence must be photographed before collection from the SOCO. Blood stains and
semen stains can be collected on sterile material and if still a liquid, should be left to dry on
the material at room temperature before they are collected in order to reduce transference.
They are then packaged (all exhibits packaged separately) and need to be transferred to a
forensic lab, preferably within 24 hours. Blood stains are stored in a labelled, sealed
container and semen stains must be carefully wrapped in paper, sealed in a polythene bag.
These are then analysed in a forensic lab for blood type and DNA markers in order to create
a DNA profile. Any individual items such as hair samples and fibres and threads are handled
in a similar but slightly different manner. Hair samples can be collected on clothing which can
be wrapped in paper, or a small tool can be used to pick up the hair and fibres & threads are
often found on their items or caught in torn materials. These must be picked up with gloved
fingers or tweezers and then sent to a forensic lab for investigation. Small fragments of hair
should be placed in paper which is marked and sealed and fibres should be wrapped in an
envelope also sealed and marked. These can be analysed under a microscope and they
undergo toxicology exams for multiple pieces of evidence. Hair samples can reveal both the
race of the individual and where the hair itself came from, and fibres and threads can reveal
the type or colour of the fabric they come from and comparisons can be made to the
suspects clothes. A case example of where hair and fibres were used was in the case of
Sarah Payne. Sarah’s hair and fibres from her jumper were found in Roy Whiting’s van.
There were also fibres on her shoe that matched the passenger seat cover in the van and
her hair was found on the sweater. Roy Whiting was found guilty of the murder. With
fingerprints, if patent and left in liquid such as blood, photographs are taken for a lasting
record. If impressed into a soft material or tissue they can be photographed or put into a
mould if they are fragile. They are stored as photographs or a mould and are put into a
database to help future cases. It also has to be ensured that they are stored in a cool, dry
place. For analysis, fingerprints are dusted with a powder or chemical agent, such as
magnesium powder or a UV light is shone in order to reveal the unique imprints. Impression
casts can be made for shoe prints or bite marks. Bite marks are transferred to a forensic
odontologist whilst show prints are transferred to a regular forensic laboratory. Bite marks
can be marked back ton the suspect, and are common in sexual assault cases. Shoe prints
can let police know what type of shoes to look for when searching a suspect's home and can
also show weight, patterns of walking and where the suspect or victim has been. When
collecting any physical evidence, it is extremely important that the SOCO’s or CSI’s will wear
a bodysuit and gloves to ensure that the evidence is not contaminated by their own clothes
or hair. Contamination of physical evidence has caused wrongful convictions in the past, for
example in the case of Barry George. Barry was found guilty of the death of Jill Dando, shot
outside of her home on 26 april 1999 and he was arrested and charged for her murder in
