Unit 23 - Forensic Evidence, Collection and Analysis
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BTEC Applied Science Unit 23 C+D Forensic Evidence
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Unit 23 - Forensic Evidence, Collection and Analysis
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PEARSON (PEARSON)
Hello, this is a D* (Distinction) grade on unit 23 C+D. This includes a witness statement, how to analyse different types of physical, biological and chemical evidence and how to come to a conclusion with all evidence found after analysing them. By reading this assignment you will understand what t...
Unit 23 - Forensic Evidence, Collection and Analysis
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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
Expert witness
Before approaching the crime, my team and I wore our PPE’s and went over a risk assessment. After
wearing our PPE and went over the risk assessment, we cordoned off the area of crime to prevent
contamination of evidence and prevent unauthorised personnel from entering and contaminating the
crime scene. My SIO discussed which search method to use with our team and we agreed to choose
Zone, Lane, and Spiral search methods because it was well suited for the crime scene. The reason Zone
was used because we had lots of investigators searching the scene so using zone would make sure it was
all organised and all pieces of evidence was easier to collect. Furthermore, the shape of the scene was a
square which made it much easier to split up into different sections for the zone. In the zones, lane
search method was used to thoroughly search each section. There was a table and chair in the middle of
the room, which made the decision to choose spiral method much easier because we would circle
around the table and slowly move towards the centre/ table from the outskirt of the crime scene. After
agreeing on the search method, my team and I photographed all items of evidence and the scenery of
the crime scene. This was to identify points of entry and where each piece of evidence was from the
cordon line. Once all photos were taken, place cards were put in the evidence items to signify where it
was and how many there were; while this was happening, an investigator was sketching the entire crime
scene from different point of views and a bird's eye view of the whole scene. When all evidence was
photographed, we packaged the items in suitable bags which prevented contamination and allowed us
to fill out additional detail about the evidence regarding when it was found and packaged, where it was
found and a description of it.
Witness statement:
Name: Date:12/07/2023
Case number: 428365 Location:
I swear I am telling the truth and nothing but the truth. I am making this statement voluntary, without
reward, promise of rewards, threat or force towards me. Everything said in this statement is from my
point of view.
I have been a practicing forensic scientist for almost a year. My first official case was on 12th June 2023
located at ... at around 11:10 am. Before entering the crime scene, my group and I put on our Personal
Protective Equipment which were:
Shoe coverings: To keep extraneous material being transported to the scene via shoes.
Full body suits with a hood: To prevent hair and synthetic fibres from falling onto the scene.
,Latex gloves: To prevent our biological evidence like fingerprints from contaminating the evidence.
Mask: To protect my team and I from inhaling any harmful chemicals or preventing us from spreading
our biological material.
After wearing the suitable PPE, my team and I cordoned off the area and recorded our names, time of
entry, location and reason for entry on a cordon log. Once we completed this, we took photos of the
crime scene. Afterwards, we moved onto discussing a method of search patterns and we agreed upon
lane and spiral to gather our evidence.
Just to clarify, the importance of wearing PPE’s, cordoning off the area and taking photos was to ensure
our safety, prevent contamination and to preserve the evidence as well as the integrity of it and finally
gathering sufficient proof to show in court to strengthen our argument.
At the scene, I found several pieces of evidence that I believe may be relevant to the case.
Biological evidence:
Blood was found on multiple occasions around the scene such as on a diary, table and wooden block;
however, as soon as I came over to collect the blood, it was already dry hinting that whatever caused
the injury was a long time ago; Hence why I took a sterile swab and carefully applied distilled water over
it to collect a wet sample to take back to my lab for analysis. Furthermore, judging from the angle and
size of blood splatter, it seems as if the drop was from a 90° angle straight above around a height of 45
cm. Once I took it back to my lab for analysis, the results I obtained gave me the conclusion that the
blood was A+.
Another item was hair fibre and several synthetic fibres. I collected the hair strand and synthetic fibres
with a pair of tweezers and inserted it in separate secure plastic evidence bag and labelled it. I analysed
these items under a light microscope with different magnifications of x40 and gradually increased to
x100 onwards for a clearer observation to identify their characteristics and determine if they were
related to the crime.
In addition, I also found fingerprints on a handheld mirror. To collect these prints, I scattered aluminium
powder over the print and gently brushed off any excess powder thus leading to me applying a
transparent piece of tape over the print to make an exact replica. In my analysis stage, I discovered the
pattern of the print was a swirl that belonged to the right thumb.
,Chemical evidence:
Moving onto chemical evidence, I found a strange white powdery substance. To analyse this substance, I
placed some in separate test tubes and heated it over a Bunsen burner while the powder was mixed
with HCl, sodium hydroxide or another chemical etc. This allowed me to determine the chemical
composition of the substance and identify any potential matches to known substances.
I also found a white paste that looked like plain toothpaste. I used a variety of chemical tests to
determine its composition and identify any potential matches to known substances.
Physical evidence:
At the scene, I found several pieces of physical evidence. One of the items was a scarf and a small red
courier bag. Another more helpful item was a 29 cm footprint made by boots, typically worn by builders,
which were size 9 Uk. This could be a huge improvement in finding the perpetrator. I also found a laptop
with the letters “kxzxg” typed in. On the floor next to the table, there was a diary opened which a girl
wrote her worried thoughts about a potential stalker. She wrote how she felt worried and scared of this
person. There was a particular page that caught my attention, where the girl mentioned a metal bat and
that the person was nearby. Another physical item was an opened textbook. There was also a small
paper note with the number 0800 1111 written on it. Lastly, there was a rectangular wooden block with
a dried blood stain on it. There was also a hair comb and hand-held mirror. Unfortunately, there was not
much found on the analysis stage, but the physical evidence has further helped identify which type of
situation the victim is in.
Based on my analysis of the evidence, I believe that it may be possible to identify a suspect in this case. I
assume it is a male with an average build, 6ft in height wearing size 9 Uk boots.
Ballistic: It is related to firearms which are classed under 3 categories- handguns, rifles and shotguns.
Ballistics also comes in 3 categories- internal, external and terminal. Ballistics is the study of projectiles
in flight. Closely related to ballistics are GSR (gunshot residue) as well as bullets, cartridges. GSR can be
categorised into two main types: inorganic GSR (IGSR), also known as primer GSR, and organic GSR
(OGSR). The extreme temperature and pressure are followed by rapid cooling when combustion
materials escape from weapon openings, resulting in particle formation of IGSR. OGSR is not formed by
the firing process. It mainly originates from propellant powders, firearm lubricants, some products of
their transformation and hydrocarbons. Forensic ballistics commonly includes providing an opinion as to
whether the ammunition components may be linked to the weapon which discharged them,
establishing range of fire, identifying entry and exit wounds, interpreting damage caused by gunshots
and examining the mechanical condition of guns. Ballistics are typically collected by hand with gloves by
an expert, reason being is to make sure that the weapon is safe, not loaded and cannot cause any harm
and so they can analyse and correctly handle these items excluding possible contamination or damage
to the evidence in order for the evidence to be scanned for prints or information as to where it
originated from. Specifically for bullets and cartridges they are handpicked so that no further marks are
made by using tweezers, as this would decreases the validity of the evidence in court. Experts can
determine the angle ballistic were fired, distance travelled and the velocity/ speed of the firearm from
thorough examination.
There were no ballistics, or traces of ballistics, found at the crime scene.
If ballistics were found, the way to analyse them is by using gas chromatography/ mass spectrometry
(GC/MS). This is a scientific process used for the identification of organic gunshot residue compounds.
Ballistic experts also use microscopy to observe the bullets for marks. For inorganic residue, methods
like neutron activation analysis and atomic spectroscopy techniques are used. Using an organic solvent,
gas or liquid chromatography (GC and LC, respectively) techniques with mass spectrometry (MS)
detection are typically used for OGSR analysis.
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