This is an in depth assignment discussing the analytic techniques used to examine biological, chemical, and physical forensic evidence, the analytic techniques used to examine biological, chemical, and physical forensic evidence, the choice of the analytical techniques used to examine biological, c...
Pearson betc level 3 national diploma in forensic and criminal investigation
Assignment 4 Unit B
P3: Describe the analytic techniques used to examine biological, chemical, and physical
forensic evidence.
Biological evidence analysis techniques:
Blood group analysis:
- Benzidine test is a reliable test used to test whether blood is present at a scene.
It will turn bluish or green if there is the presence of blood, as the benzidine will
oxidise revelling the colour.
- Luminol test is used as a presumptive test for blood, it can be used to determine
if there was blood present at a cleaned crime scene. It is chemiluminescent and
produces a blue glow when it reacts with the iron atoms present in haemoglobin.
- Kastle-Meyer test is made up of a solution of phenolphthalein which helps
determine the presence of blood, it will turn pink if there is any present. It does
this by reacting with the activity of the peroxide in haemoglobin.
Genetics (DNA sequencing, genetic profiling):
- Genetic profiling which is also known as DNA profiling is a technique that is
used to help in the identification of any samples gathered on a crime scene, this
can also be helpful in identifying individuals involved in the crime.
Latent fingerprint enhancement and visual examination (four basic patterns, minutiae
and ridge counting):
- Four basic patterns:
- Arch: This is when the ridges run from one side to the other aide making an arch
patten. These only make up 5% of recorded fingerprints, there is two types of
arch fingerprints plain arch (ridges runs from side to side making a hill pattern)
and tented arch (the hill pattern starts on the left side of the finger).
- Loop: This is when the ridges enter from the same side recurving over each
other. These are about 65% of the population's fingerprints. There are two types
of loop fingerprints radial loop (when the loop starts on the thumb side of the
hand) and ulnar loop (when the loop starts on the little finger side of the hand).
- Whorl: This is when the ridges form a pattern that can be a spiral, oval or circle,
it is simple to identify and makes up about 35% of the population's fingerprints.
- Composite: This is a combination of all the other fingerprint types. They are
central pocket loop (combination of whorl and loop), lateral pocket loop (this is a
combination of two loops) and accidental (this is a pattern that doesn’t fit into any
of the other categories).
, - Minutiae and ridge counting: This is a technique that is where the ridges on a
fingerprint are counted to help identify which pattern it is. It is mainly used to help
with the classification of the pattern and to help improve the efficiency of the
identification.
Hair identification and analysis (microscopy):
- Hair identification and analysis is needed as mainly during violent crimes
piece of hair or fibres can transfer from the perpetrator to the victim or vice versa.
It also needs to be used in case the hair gathered is actually animal hair and not
human hair. They use microscopes to determine whether the hair has naturally
fallen out or whether it was pulled, they do this by figuring out if the hair is
anagen phase (growing) or telogen phase (resting).
Bone and skeletal physiology:
- Skeleton and bone analysis in forensic science can be used to help determine
the circumstances or possible cause of death of the victim. It can also be used to
help identify a victim if that is not known as they can compare the skeletal
pathology of the victim to medical records to help with the identification. When
examining the skeleton of a victim if there is any form of trauma to it than the
cause of death can be determined.
Control samples:
- Control samples are any sort of forensic evidence that is gathered from a crime
scene that can be sued to ensure that any analysis on the samples is performed
well enough to produce reliable results. So, for example a biological control
sample would be blood found on a possible victim or recovered from a crime
scene.
Reference materials:
- Reference materials are used to help forensic laboratories validate the
analytical methods that they use to test different evidence gathered and to also
make sure that the results gathered are accurate.
Chemical evidence analysis techniques:
Chromatography (paper, column, TLC, GC, HPLC):
- Paper chromatography is a technique that is used for separating dissolved
chemical substances by using viewing their different rates of migration across a
sheet of paper.
- Column chromatography is a method that is used to separate the substances in
a mixture, like drugs, it does this by passing the mixture though a column packed
with a specific type of absorbent, and it will then provide the substances, liquid or
solid.
- Thin layer chromatography is similar to paper chromatography but instead of
paper, the stationary phase is a thin layer of an of a surface insert which is
supported on a flat unreactive surface.
- Gas chromatography is different from regular paper chromatography as the
mobile phase is a gas insert and the stationary phase is a very thin layer of an
insert of solid support.
- High performance liquid chromatography is usually when the mobile phase is
mixed with a solution like methanol to enhance the separation.
Mass spectrometry (spectrometric technique):
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