Unit 23 - Forensic Evidence, Collection and Analysis
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This assignment contains all of the necessary contents such as different roles of authorised personnel in the crime scene, types of search patterns, types of method used in the crime scene such as casting, brushing and swabbing. In overall, I have achieved distinction grade on this assignment and w...
Unit 23 - Forensic Evidence, Collection and Analysis
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Mohammed Salam Unit 23: LA A
UNDERSTAND HOW TO GATHER FORENSIC EVIDENCE, THE INTEGRITY TO FORENSIC
INVESTIGATION AND THE IMPORTANCE OF HEALTH AND SAFETY
Introduction:
In my report, I will be discussing about the roles of each scientific support unit, justifying the
importance of preserving and gathering forensic evidence and the integrity to forensic investigation
and the importance of health and safety.
Restriction of the scene and restriction of access:
The security of the crime scene is the most critical component of evidence collecting and
preservation. This is done to safeguard the relevant evidence until it can be recorded and collected.
The condition of physical evidence when it is acquired can make or break a case's prosecution. The
scene is guarded from the arrival of the first police officer on the site until it is released from police
custody. There will be a limited number of authorities allowed to enter the crime site in order to
protect the evidence.
Observing and recording the scene:
A methodical and patient approach should be taken by investigators before analysing the crime
scene, as much information as possible should be obtained so that valuable and fragile evidence,
such as shoeprints and trace evidence, will not be destroyed. An analysis of the crime scene is
initiated after collecting all the facts. Every aspect of the crime scene investigation should be
documented with detailed notes and time stamps, and a walk through the area following the 'trail'
of the incident is usually the starting point of a crime scene investigation. Criminal activity takes
place on the trail, which is usually marked by physical evidence. This might include the point of
entry, the crime scene, any areas cleaned up by a suspect, and the escape point. It may become
necessary to conduct a walkthrough in certain situations if potential evidence is in danger of
destruction. This evidence should be preserved, documented, and collected as soon as possible in
such situations.
Identifying and targeting evidence:
Physical evidence at crime scenes can be used to identify the suspects or suspects as part of criminal
investigations. Identification and targeting of evidence are crucial to the success of criminal
investigations. Evidence should be marked when observed so that others will not step on it.
Witnesses or victims may provide evidence that identifies the accused as the perpetrator of a crime.
These images are taken from descriptions provided by witnesses to crimes. The police use them as a
tool to determine the identity of a suspect during criminal investigations.
The value or probative quality of the physical evidence is used to determine what is considered
evidence in a crime scene investigation. Everything that ties a suspect to a crime scene is considered
physical evidence. Blood, body fluids, hair, and tissues are examples of physical evidence that can be
retrieved at a crime scene. The investigator creates a space that is large enough to contain all
physically pertinent evidence that may be present, and then constructs a theory about what type of
crime took place in order to predict what evidence might be present. The SOCOs uses their expertise
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,Mohammed Salam Unit 23: LA A
and knowledge for the investigation to identify and gather the piece of evidence. The SOCOs will use
variety of forensic tools and procedures to identify the prosecutor and obtain the evidence like DNA
analysis, fingerprints and digital evidence like phone records, emails and internet logs.
The preservation and integrity of fragile evidence is ensured by collecting it first. It is crucial to
collect evidence carefully and extensively so that fragile materials are not destroyed while critical
evidence is collected. First, crime scene investigators may collect hairs, fibres, and fingerprints while
peeling back each layer of evidence one at a time, starting with the most fragile. The most fragile are
collected first since it can be contaminated easily. To ensure that evidence arrives undamaged and
uncontaminated, damaged, or spoiled at a crime lab, it should be packaged in a suitable type of
package. The long – lasting evidence can be collected after the most fragile evidence, evidence like
weapons and clothes are long – lasting evidence. If the evidence is fragile or easily lost, it should be
collected and packaged in its entire form, if size and circumstances permit. The evidence must be
labelled appropriately so that it can be identified and followed throughout the investigation. As a
result, it is critical to gather weak evidence first in order to assure its preservation and integrity. The
SOCOs collaborate with the CSIs to ensure that evidence is acquired and managed in such a way that
it regulates credibility and is presentable in court.
Documenting and recovering trace materials:
It is imperative that SOCOs document the crime scene before any evidence is moved or collected,
including taking detailed, accurate, concise, readable, and specific notes containing the names and
signatures of SOCOs. A sketch should include rough measurements and directions, as well as a key
and north line indicating the direction. Taking photos of the entire scene and surrounding area, as
well as entry and exit points, can provide a clear overview of the scene and its surroundings. The
photos must be taken before the transportation of the evidence. To document the details, close-up
images of the evidence are taken, along with a measuring scale to show the item's size. Videos are
often incorporated into the photos in order to create a more accurate representation.
Characterisation and comparison:
Characterisation and comparison are mostly used in forensic science for analysing physical and
biological evidence, these methods play important roles in forensic science for evidence analysis and
identification. As part of the criminal investigation, characterisation is used to identify and defining
the evidence’s characteristics like its age, origin, and composition. Through analysis of physical and
chemical properties, characterisation determines the distinguishing characteristics of evidence.
When ridge patterns, ridge widths, and pore structure are characterised, fingerprint profiles are
generated that can be compared for fingerprint analysis purposes. When analysing DNA sequences
for characteristics, specific genetic markers may be examined to determine similarities and
differences among samples.
Comparison in forensic science is the procedure of comparing two specimens to discover if they
have a common origin by undergoing the same tests and examinations. The comparison method is
used in forensic science to connect evidence to suspects, victims, or crime scenes. To determine
whether different physical and biological evidence matches, forensic scientists conduct comparison
analysis on fingerprints, DNA, weapons, tool marks, and trace evidence. To assess if two cartridge
cases or bullets were discharged from the same gun, firearm examiners use a comparison
microscope to compare two cases or bullets.
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, Mohammed Salam Unit 23: LA A
It is crucial to characterise and compare data and evidence before assessing their trust and
authenticity. Forensic document examiners are trained to uncover and identify features of
documents that could be used to confirm the authenticity and trust of the data. During forensic
image comparison, at least one variable is captured in an image, and it is evaluated to determine
whether there is a similarity or difference between the images. During the capture, processing or
editing of an image, experts must evaluate and recognize the conditions and limitations that
impacted the appearance of subjects or objects depicted in order to be able to accurately interpret
its content.
Marks and impressions:
Footwear impressions, tyre marks, tools, and other markings made by objects leaving behind
impression evidence include indentations and prints left behind when two objects come into
contact. Footwear impressions might be left on surfaces by people when they step. These
impressions could consist of two-dimensional prints in deposited material or three-dimensional
prints in softer surfaces. While non-destructive procedures should always be used first, if possible,
there are numerous options for improving and recovering footwear imprints.
Prevention of contamination
Individuals can contaminate the crime scene and evidence at any stage of investigation. The
contamination is the unwanted transfer of material. Contamination in evidence is defined when an
unwanted foreign substance is introduced to the evidence source. The foreign substance like DNA,
dirt or soil contacts with the evidence will be considered as contamination. It is important to avoid
the contamination since it can compromise the evidence and may not be longer used against as
evidence. The contaminated evidence is considered useless since it can lead to inaccurate results
and miscarriage of justice.
Here is a table which states how evidence can be compromised through contamination and how the
contamination be prevented.
How can the evidence be contaminated? How can it be prevented?
Using the same equipments from previous Disposable and new sterile equipments should
crime scenes to obtain the evidence. be used every time when attending to every
crime scene. These equipments can include
scissors, swabs, and tweezers.
Two or more evidence placed in the same Ensure that the evidence source is placed in a
evidence packaging results in cross – suitable and separate packaging.
contamination.
Package that are unsealed after placing the Ensure that when placing the evidence, select a
evidence source. suitable type of packaging required to store the
evidence source, ensure that packaging type is
not obstructed and should be sealed carefully.
The authorised personnel in the crime scene Ensure before entering the crime scene you
leaves their hair, DNA, fingerprints, footprints, must not bring your personal items. Eating and
and fibres. drinking at crime scene is prohibited and should
be avoided at all times in the crime scene. Wear
full PPE before entering the crime scene the
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