Unit 23- Forensic Evidence, Collection and Analysis
Learning aim A: Understand how to gather forensic evidence, the integrity to forensic investigation
and the importance of health and safety.
Gathering and preserving Forensic Evidence
P1
Restriction of the scene and restriction of access:
Once the SOCO/CSI gets on the scene, a variety of security and safety concerns must be addressed
before the scene or evidence can be examined. Access must be controlled to prevent evidence from
being destroyed or contaminated. As a result, only authorised workers are permitted to enter the
crime scene using a common route approach (CAP). This Is where there authorised personal enter
from one entrance and exit from another designated exit. Barrier tape, cars, and guards are used to
construct a police cordon that encircles the crime scene. A logbook is also kept tracking who enters
which include their role, name and entry and exit time.
This procedure is necessary in order to prevent any contamination or damage to potential evidence.
The consequences for incorrectly restricting the scene could be wrongfully imprison someone since
if the scene was not redistricted someone could walk into the scene contaminating it which the
prosecutor could use as evidence against them.
Observing and recording the scene:
The SOCO/CSI conducts a risk assessment to identify any health and safety problems and to ensure
that the whole forensic team is aware of any dangers and how to reduce the risk of injury.
Authorised personal may attend the scene when a risk assessment has been completed.
Recording and observing the scene is necessary for the health and safety of the workers so they
don’t get hurt when performing their job. The impact of incorrectly following the procedures would
be that someone could get hurt when performing their job.
Identifying and targeting evidence:
To minimise distortion and motion blur, the video should avoid any extreme angles or turning. The
technician should also not digitally zoom in, instead photographing any object of interest. The
purpose of the video is to get a roughly 3-dimensional room of the scene at the time of the crime,
which will help later with identification.
When the items of interest have been proportionately photographed, the priority of evidence
collecting must be determined. Fingerprints and blood, for example, are very time sensitive due to
their volatility and ease of contamination, making them a high priority for collection and would be
gathered as soon as feasible. The crime scene may also be exposed to environmental variables like
as rain or severe temperatures, which may destroy evidence such as footprints or tire marks so they
would be next.
This procedure is necessary because without the priorisation of evidence you might lose some vital
evidence which could be the committing evidence. The impact of incorrectly following the procedure
could be that the criminal wouldn’t get prosecuted because there was a lack of valid evidence
because it got damaged or contamination due to not prioatising the evidence.
Documenting and recovering trace materials:
Firstly, the SOCO records the crime scene before any evidence is moved or collected, there are 4
ways of recording evidence these include:
, 1. Sketches
2. Photographs
3. Videography
4. Note-taking
The information recorded by the SOCO include the following:
Date and time of examination
Crime case number/police reference
Location/address of crime scene
Detailed description of crime scene
Location of items of evidence
Description of evidence including evidence item/exhibit number
Time of discovered and sketch of evidence
Description of evidence collection and packaging techniques including evidence bag number and time
of collection
Storage and transportation information. (1)
This procedure is necessary in order for the investigation to come back later and look at the
placement of the evidence so they can get an idea of what happened and where it happened also. It
can also be called up for evidence in court to help in convicting the proprietor. The impact of
incorrectly following the procedure would be that an attorney would bring the misuse of
documentation into question which could lead to an acquittal because of the poor documentation.
Marks and impressions:
According to Locard's theory, "every contact leaves a trace," hence every contact may be gathered
and analysed to determine who committed the crime. Impression evidence includes any markings
left behind when one thing comes into contact with another, such as an indentation or print.
Impression evidence includes footwear impressions, tyre marks, and markings created by tools and
similar objects. Impression evidence may be gathered in a variety of methods, but the most typical
are casted items such as in tyres or footprints. Mark evidence is evidence that leaves an impression,
scratch, or abrasion when it comes into contact, such as scratching. Because the markings fade over
time, photographs would be used to capture them.
This procedure is necessary to any investigation because it would help link a suspect to a crime
scene because if a footprint mark matches with the suspect then they could get committed to the
crime. The impact of incorrectly following the procedure would be that the subsect might not be
committed with the crime since there would be a loss of evidence if the marks and impressions
weren’t recorded correctly.
Prevention of contamination:
At all costs, contamination must be avoided. Individuals can contaminate the investigation at any
step. Furthermore, cross-contamination between various pieces of evidence might occur at any
time. Evidence that is deemed tainted cannot be presented in court and may call into doubt the
integrity of other pieces of evidence, perhaps leading to acquittal or incorrect conviction.
SOCO/CSI- Wear full PPE such as gloves, suit, mask and overshoes.
Unsealed package- ensure no holes where evidence can escape or enter.
Old equipment- use new sterile equipment and use disposable equipment at each scene.
This procedure is necessary because it would allow the person who committed the crime to be
caught and brought to justice. The consequences for not following the procedure would be that an
, attorney would bring the contamination into question resulting in the person going free and if
contamination occurred it would destroy the evidences value to catching the criminal.
Methods of collection (casting, swabbing, hand picking, taping, brushing, vacuuming):
When evidence is located at the scene, it is photographed in place with an evidence scale and
documented before being retrieved. The CSI must describe the evidence, including its description,
location, and time of collection, and assign it a unique evidence/exhibit number.
Vacuuming method- The suspected sample location is hoovered up and collected in a filtered trap
connected to the vacuum. For submission to the laboratory, these samples are enclosed on clean
trace paper. Vacuuming is the least desirable method of collection since there is a possibility of cross
contamination if the equipment is not thoroughly cleaned between uses.
Hand picking method- This approach entails visually inspecting an object for traces of evidence such
as hairs, fibres, glass, soil, and paint. In the search, normal room illumination, oblique lighting, and
an additional light source can all be utilized. A magnifying lens might also help the examiner in
finding evidence.
Casting method- Casting involves the use of a powdered stone material, such as dental stone, that is
combined with water and poured into the imprint. When it dries, it forms a three-dimensional
replica of the imprint. Imprints and impressions can be enhanced to bring out more subtle features.
Swabbing method-
Taping method- Taping involves using clear sticky tape or gel lifters to the site where evidence is
located and this picks up trace evidence such as fingerprints, fibres and hairs.
This is extremely necessary procedure since it is how evidence gets collected and then analysis. So,
without this procedure criminals wouldn’t get charged since the lack of evidence. If evidence is not
correctly collected, then it could let the perpetrator who committed the crime since any attorney
could suggest the mishandling of evidence which could lead to the acquittal of the trail.
Storage and transport of evidence that preserves the integrity of the evidence:
When evidence is gathered, it must be carefully and securely delivered to the evidence storage and
forensic laboratory. The SOCO will carry the evidence back to the police station/forensic evidence
store and book it in, providing an audit trail and documentation of each use, this is to ensure the
continuity of evidence. From here, the evidence is sent to the appropriate forensic laboratory for
analysis, through a reliable and secure courier or police officer(s).
The evidence must be kept safe at all times to prevent unapproved access from removing or
tampering with it. It is critical that the evidence be stored in appropriate conditions while in storage.
This evidence must be retained and safeguarded from degradation and contamination.
This procedure is necessary since it keeps the integrity of the evidence so it can be used as vailed
equipment. The impact of not following the procedure would be that the evidence would most likely
be unusable since if there was no documentation behind every evidence the attorney could say that
contamination could happen and then it would dismiss it as evidence no matter how important it
was.
Continuity of evidence:
A log is also kept that shows who has access of the evidence at each step of the criminal
investigation - this is documented on the evidence bags, boxes, or a label securely attached to the
evidence. This is to make sure that there is no chance the defence attorney can state possible break
in the continuity leading to an acquittal.
