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Unit 23 part C and D
- Institution
- PEARSON (PEARSON)
Written during the 22/23 Academic season
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Hamza SheikhQualification Pearson BTEC Level 3 National Diploma in Applied Science
Pearson BTEC Level 3 National Extended Diploma in Applied Science
Unit number and title Unit 23: Forensic Evidence, Collection and Analysis
Learning aims:C: Conduct scientific analysis of physical, biological and chemical evidence, D: Be
able to justify methods, interpret findings and report on conclusions of forensic techniques and
analysis
Assignment title ‘Expert witness’
Vocational Scenario or Context:
As a trainee Forensic Technician working for the British Transport Police’s Scientific Support Unit. As
part of my training my supervisor has set up a simulated crime scene. You are to act as an ‘expert witness’
and analyse the evidence sent to me from the crime scene, drawing conclusions and reporting on my
findings. You will be asked to present my conclusions about the evidence to a ‘mock court’. My supervisor
will observe me while I carry out my laboratory work and will record my presentation to the court,
providing ‘cross-examination’ of the evidence you present to test my evaluative skills. The supervisor will
use all of this information to decide whether or not you are now competent to move into the laboratory to
carry out live investigative work.
Contents page:
The methods utilised to undertake scientific investigation of physical, biological, and chemical data are
the most crucial information in this text. Physical evidence techniques include ballistics, ballistic
fingerprinting, propellants, microstamping, cal. tracers, genetics, fingerprints, hair and fibre
identification and analysis, microscopy, bone and skeletal physiology, and toxicology. Chemical evidence
techniques include instrumental analysis, visual examination, presumptive tests, chromatography,
spectrometry, chemical presumptive tests, chemical enhancement. Ballistics, ballistic fingerprinting,
propellants, microstamping, calibre wound patterns, trajectory, footwear, oblique lighting, casting,
electrostatic lifting, gel lifting, visual analysis and comparison, tool marks, documents, handwriting, IT,
and other fields of science are examples of physical evidence procedures, The learning objective is to be
able to defend approaches, understand results, and communicate conclusions from forensic procedures
and investigation. The use of forensic science in England and Wales, the Forensic Science Society (FSS)
archives, and forensic science accreditation all fall under the category of drawing reasonable and
balanced conclusions from observations of the crime scene, test results and measurements, probability of
validity, reconstruction of events, court case preparation and verbal presentation of evidence, expert
witness statement and opinion, and forensic science.
, Hamza Sheikh
C. P5 Explain the techniques used in forensic science to analyse physical, chemical and biological
evidence.
In forensic science, certain techniques are used to analyse multiple evidence which differ from
each other for example the 3 categories that are up to analyse are biological, chemical and
physical, reports of the evidence will be in great detail outlining the fundamental core principle
of why the techniques are used and what they do to help with evidence analysis. [1]
Biological evidence analysis techniques:
Blood group analysis: Analysis of the blood groups is a frequent measure that is taken in the
forensic laboratory, this because blood is the most common bodily fluid found within the crime
scene, due to the fact there can be multiple spillages in different types of crime scenes ranging
from burglary to murderer. Forensic serology assessed by analysing and examining the crime
scene’s blood or the blooded item which can be taken in for evidence. Blood is utilised in
forensic analysis to identify individuals accused of specific sorts of crimes, because an
individual's blood type is unaffected by illness, medications, the environment, occupation, living
circumstances, or any other physical scenario, forensic scientists routinely use blood typing
procedures.Multiple techniques are used within the laboratory by forensic scientists, for
example colour tests which are presumptive that provides provisional results that are
non-conclusive, certain chemicals will be used such as phenolphthalein that is used by forensic’s
scientist to get a reaction between the chemical and the blood’s heme molecule. Colours may
determine if the molecule is present, in particular a pink colour shows that the sample is
positive for the heme molecule whereas blood that is white has a combination of a red brownish
colour when reacting with the chemical. [1][2]
ABO blood typing:
The ABO blood type system is made up of two antigens and two antibodies found in human
blood. The two antigens are antigen A and antigen B [2]. The two antibodies are antibody A and
antibody B. Antigens can be discovered on red blood cells and antibodies in serum. Based on
their blood antigen qualities, all humans can be split into four groups: those with antigen A
(group A), those with antigen B (group B), those with both antigen A and B (group AB), and those
with neither antigen A nor B/group AB, known as group O [2]. The table below indicates which
blood groups have particular antigens, as well as which antigens respond with which antibodies:
, Hamza Sheikh
Blood group Antigens present Reaction with antibody Reaction with antibody
A B
A Antigen A Yes No
B Antigen B No Yes
AB Antigen A and B Yes Yes
O No antigens found No No
Genetics: DNA sequencing is a laboratory technique which is generally used to find out multiple
types of sequences such as those of nucleotides or bases within the molecular portion of the
DNA strand. The bases’ sequence is where the cell’s biological information is concealed, this is
important within forensic science as many other parts could be understood and analysed such as
understanding the bases may give out information on other genes. DNA sequencing will be
conducted by the PCR method, Step 1: Making the template into single strands via denaturation,
Step 2: To attain a new strand synthesis, primers will be annealed to the original version of the
strand, Step 3: The replicated version of the primers’ DNA strands are extended. [3][4]
Genetic fingerprints is a laboratory technique that instantly detects the large traces of
minisatellites within the genome, leading to a unique pattern being formed of the individual and
their genetic makeup. To gain DNA fingerprinting, 6 steps are required, Step 1: extraction of a
boldly fluid(mainly blood), Step 2: Adding restriction enzymes, Step 3: Electrophoresis, Step 4:
Transfer to the membrane, Step 5: Incubation with probes that are labelled, Step 6: X-ray. [5]
Fingerprints four basic patterns: Loop - The most common type, ridges come in from a side
then curve round to allow the ridge to exit out of the same side of the finger, Arches - a print
which is simple yet rare, the flow of the ridge is coming in from one side, then caressing up and
over like a wave, the ridge stops its flow by exiting from the other side of the finger, Whorls - the
print is complex as the ridges curve in a shape of a circuit which is complete, Composite - its
when a pair of patterns merge, however it can also be a pattern which is unusual. [1]
, Hamza Sheikh
Fingerprints ridge counting - method that occurs when there is a loop pattern present, the
method includes counting the ridges present, to enable this method to occur, 3 features must be
identified, delta (Friction ridge point), Core (Fingerprints centre area), Type lines (2 Innermost
ridge.) [1]
Loops Arches Whorls [1]
Fingerprint Minutiae - Minutiae points are the points on a ridge that appear when it becomes
discontinuous. A ridge can either end, which can be referred to as termination, or split into two
ridges, which is defined as bifurcation. [20]
Hair and fibre identification - Hair is a common form of forensic evidence due to the fact that
they shed quite easily, statistics have shown that 100 strands of hair are shed by an individual
onto clothes and environment. Hair could be indemnified by a microscope which could look up
to 3 different sections of the hair, these are: Cuticle which is the covering that provides the hair
with protection from chemicals, also it allows for the hair to retain its structural features. The
cuticle provides 3 distinct patterns, the coronal, imbricate and spinous, these patterns allow for
determination of species. [1]
DNA sequencing - Forensic investigators utilise DNA sequencing as a potent tool to pinpoint
criminals. It involves collecting samples of blood, sperm, hair, and other bodily fluids from a
crime scene and amplifying them so that they may be used in authentication tests to look for
specific DNA sequences. It is a trustworthy and precise method of identifying people and
offering important proof in criminal investigations. [1]
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