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What is Evidence?
Can be defined as information that is given in a legal investigation, to make a fact or propositions more or less likely.
What are the key forms of evidence in court?
Testimonial, documentary and physical, digital, demonstrative
What is testimonial evidence?
refers to eyewitness statements made under oath or affirmations
What is a competent witness ?
A witness who gives facts about that case as they have the mental capacity to understand the question put to them.
What should competency not be confused with?
Credibility and reliability
What are the factors affecting eyewitness testimonies?
Weapon focus, internal factors (stress), external factors (leading questions), post event factors (new information)
What are the things to consider about eyewitness testimonies?
-type of crime
-how witness saw it
-interviewing techniques used
-time lapse between incident and testimony
-has the witness already identified the suspect or a diffferent individual
-relationship
What is documentary evidence?
Any document produced for the inspection by the court as evidence of its contents. It could also be any evidence that contains a record of some kind and builds up the documentation of the events leading to the crime often presented during the trials
What are examples of documentary evidence
Diaries,letters,contracts and newspapers
What is physical evidence?
Any material item that would be present at the crime scene, on the victim or found in a suspects possession
What form can physical evidence be in?
Any form such as small, large, microscopic or odour
When does the role of the forensic science begin ?
Begins at the crime scene
What is meant by a crime scene ?
Any location that is searched for physical evidence
Do all crimes have a crime scene ?
Yes
How many crime scenes can an incident have ?
Multiple
What is the order of events for forensic science in a criminal investigation ?
-recovery and continuity of evidence
-laboratory work on physical evidence
-interpretation and evaluation of evidence and presentation of findings in court
Who sends evidence for analysis in a lab ?
Soco’s
in what form is forensic evidence presented in court ?
Expert witness document
What is continuity of evidence ?
chronology of who have been responsible for its safekeeping and appropriate handing (chain of custody)
What measures are taken to prevent tampering of evidence ?
-tamper-evident seals on evidence packaging
-dedicated secure evidence storage facilities
-secure contemporaneous note taking
-uninterrupted chain of custody
-minimizing the number of people in the chain of custody
What measures are taken to prevent accidental contamination of evidence ?
-SOPs that incorporate anti-contamination measures:
-the isolation of bulk and trace evidence
-the use of PPE
-the decontamination of surfaces between samples
-isolation of samples between victims and suspects
-re-packaging every samples as soon as it has been analyzed
What measures are taken to prevent deterioration ?
-appropriate packaging and storage
-assiduous logging and note taking
When would evidence be deemed inadmissible ?
If continuity of evidence cannot be adequately demonstrated, as the loss of its integrity cannot be ruled out
What is evidential value ?
How useful an item is in telling us something
What helps determine evidential value ?
-has a crime been committed
-Identity
-link suspect or victim to each other
-establish a connection between different crime scenes
-corroborate or refute evidence from another source
Once the evidence has been analyzed what can the scientist do ?
-interpret: ascertain what may be established about the nature of the item
-Evaluate: the data obtained to establish whether it supports the prosecution or defense proposition
What is Streamlined Foresnic Reporting (SFR) ?
-multi-step process
-standardised form to report the outcomes of crime scene processing and laboratory analysis to the police, defence, prosecution
How do expert witness statements have to be written ?
In layman’s terms and be easily understood by non-scientists within the criminal justice system
What are common types of evidence ?
-direct
-circumstantial
-associative
-reconstructive
What is direct evidence ?
Eyewitness statements and confessions
What is circumstantial evidence ?
Evidence which is inferred from a set of circumstances that relate to the event
What is associative evidence ?
Any evidence that ties a suspect to the crime scene, victims or other evidence
What is reconstructive evidence ?
Any evidence that allows investigators to gain an understanding of the actions that took place at the scene
What is rebuttal evidence ?
Evidence offered to disprove or contradict the evidence presented by an opposing party
What is primary facie evidence ?
Evidence that will establish a fact or sustain a judgement unless contradictory evidence is produced
What is exculpatory evidence ?
Evidence tending to establish a criminal defendants innocence
What must evidence be for it to be accepted in court ?
Relevant and admissible
Whose opinion is accepted as evidence in court ?
Expert witness
What are the main categories for physical evidence ?
Trace and contact evidence
Biological evidence
Impression evidence
Chemical evidence
Other
How is physical evidence utilised ?
-provides a investigative lead for a case
-ties one crime to a similar crime or connects one suspect with another
-corroborates statements from witnesses to or victims of a crime
-the elements of a crime help to determine what will be useful as evidence
What did locard’s exchange principle say ?
‘Every contact leaves a trace’
What does the transfer of evidence depend on ?
-pressure applied
-number of contacts
-how easily it transfers
-form of evidence
-how much of the item is involved
What does evidence persistence depend on ?
-what the evidence is
-location
-environment
-time from transfer to collection
-activity of or around the evidence
What is contamination ?
undesired transfer of information between items of evidence
Which type of evidence can be readily transferred ?
Trace evidence
What does trace evidence allow provide ?
Evidence of association
What are the implications of re-transfer ?
-great care must be taken to avoid possibly cross-contamination
-the possibility of transfer subsequent to the primary transfer must be taken into account during the interpretation of trace evidence
-trace evidence can be readily lost
What is a visual way to present the results of trace evidence analysis to show the occurred transfer ?
Transfer diagram
What is evidence identification ?
The examination of the chemical and physical properties of an object and using them to categorise the object as a Member of a group
What is an example of evidence identification ?
Deterring that a small coloured chip is automotive paint
What does evidence identification help do ?
Refine the objects identity and its membership in various groups
What are class characteristics ?
features that place the item into a specific category
What are examples of class characteristics ?
-blood type
-make and model of firearms
-shoe print pattern of new shoes
What are individual characteristics ?
features that distinguish one item from another of the same type
What are examples of individual characteristics ?
-fingerprints
-strict action marks of fired bullet
-DNA
What does individualised mean in terms of evidence identification ?
If an object can be classified into a group with only one member
What is qualitative analysis ?
Information that can provide evidence about the identity of an entity
What is Quantitative analysis ?
Establish amount or concentration of a substance
What is comparison of evidence ?
comparison of evidence is done to try and establish the source of evidence. The questioned evidence is compared with objects whose source is known
What types of comparison of evidence is there ?
-different scenes
-database
-controls
-test impression
What is comparison between different scenes ?
Comparison between two pieces of evidence obtained from different places
Why do forensic scientist compare evidence between different scenes ?
To determine whether two pieces of apparently similar forensic evidence may have come from the same source
What can comparison between different scenes tell us ?
If there is any possible links between the two separate locations from which the evidence has been retrieved
What is needed to perform comparative analysis between different scenes ?
-2 or more samples
-a questioned and a known sampled
What is comparison using databases ?
Comparison between an evidential object and a relevant database
How are databases used in comparative evidence ?
to identify a category to which an item of evidence belongs by establishing its class characteristics
What are examples of suing databases ?
-bodily fluids or tissues for DNA profiling (nationals DNA database )
-fingerprints (IDENTI)
How are controls used in comparative evidence ?
Comparison between questioned samples, both positive and negative controls and reference collections
What is a questioned sample or unknown ?
A sample of unknown origin, usually collected at the crime scene
What is a known/ control sample ?
A sample of known origin is similar to a positive control sample, which is a known sample used to compare and confirm identity of questioned samples
What is a negative control sample/ blank ?
A sample used to test the chemical and or equipment for contamination
What is a reference collections or standard ?
A known sample used to test the chemicals or equipment or to compare with unknown samples
How are controls used in comparative evidence ?
Comparison between questioned samples, both positive and negative controls and reference collections
What are positive and negative controls ?
Used to evaluate hypothesis
What is an example of an hypothesis ?
-suspect is detained and detains a white powder
-hypothesis is that it’s cocaine
-results from the analysis can be compared to the results from the analysis of the known sample (positive control)
-analysis can be carried out without questioned sampled to test for contamination
How are test impressions used in comparative evidence ?
Comparison between a scene impression and a test impression
How are impressions made ?
Can be made by recognisable objects such as footwear, tyres and tools
What is the general scheme for analysing an item of evidence to determine its potential source ?
-collection and preservation of the evidence item
-collection of putative reference source material-known/control
-selection of class and individualising traits from the evidence item
-comparisons of evidence and reference
-common source for evidence and reference or different sources for evidence and reference
A t-shirt has stains that look like blood, a test is run that is negative what happens next ?
-run a different presumptive test and see if the results change
-run the first test on a sample that is known to be blood that should yield a positive result (positive control )
-run the first test on some fibres from the shirt that have no stains on them (negative control)
What three questions does the examiner consider when inferring a common or different source ?
- Do unexplainable differences exist that convince me that the items compared originate from different sources ?
- Do the quantity and quality of the class characteristics convince me that the items could originate from the same source
- Do a sufficient number and quality of individualising traits exist to convince me that they originate from the same unique source
What is cognition ?
the mental process of acquiring knowledge and understanding through thought, experience, and the senses.
What do cognitive processes include ?
Cognitive processes include mental shortcuts (heuristics), which speed up decision making.
What would happen if we didn’t have heuristics ?
Decisions would take too long
What is a cognitive bias ?
is a systematic pattern of deviation from rational judgement and from a strictly objective evaluation of sensory input or data. (Set heuristic)
What does an individuals construction of reality do ?
dictate their behaviour in the world.
What do cognitive biases lead to ?
perceptual distortion, inaccurate judgment, illogical interpretation, and decision-making.
Why is it important to guard against bias in forensics ?
Errors in the process can lead to miscarriages of justice, such as wrongful conviction, traumatic experiences for witnesses or the failure of conviction to convict dangerous perpetrators
What is anchoring bias ?
the common human tendency to rely too heavily, or “anchor,” on one trait or piece of information when making decisions.
What is confirmation bias ?
the tendency to search for or interpret information in a way that confirms one’s preconceptions.
What is the framing effect ?
drawing different conclusions from the same information, depending on how that information is presented.
What is status quo bias ?
the tendency to like things to stay relatively the same (see also system justification).
What is the role effect ?
an expert is being engaged by either the prosecution or defence team.
What is attentional bias ?
implicit cognitive bias defined as the tendency of emotionally dominant stimuli in one’s environment to preferentially draw and hold attention.
What is the bandwagon effect ?
the tendency to do (or believe) things because many other people do (or believe) the same. Related to groupthink and herd behaviour.
What is the reconstructive effect ?
when people use what they believe should have occurred to complete gaps in memory.
What is the halo effect ?
the tendency for a person’s positive or negative traits to “spill over” from one area of their personality to another in others’ perceptions of them.
What is false consensus effect ?
the tendency for people to overestimate the degree to which others agree with them.
What is just-world phenomenon ?
the tendency for people to believe that the world is just and therefore people “get what they deserve.” _ similar to victim blaming
What led to the error in the Madrid station bombing ?
Confirmation bias
What’s important for fingerprint analysts that can subject them to cognitive bias
- Fingerprints from two people can’t be identical but can be similar
- Particularly true for latent prints that are smudged or partial so differentiating features aren’t as obvious
- The significance of looking at the suspect fingerprint in detail first BEFORE seeing the target for a match is that the analyst would not have focused their observations ONLY on the similarities.
What steps could avoid cognitive bias and evidential errors with fingerprints?
An important approach in fingerprint analysis is to actively look for any differences, however small, that could exclude two prints from being a match.
How many points have to match to confirm an identical fingerprint ?
16
What was Dror et al’s experiment on ?
showed the influence of cognitive bias at the stage of verification or peer review. The source of bias was unnecessary contextual information.
What was Dror et al’s method ?
-Five experts were asked to re-examine a single pair of prints which had been examined previously in their own caseload.
-All experts had previously judged this pair to be a match.
-However, it was presented to them again as if it were related to the Madrid bomber case, a notorious case of an erroneous identification.
What were the results of Dror et al’s study ?
Four out of five experts changed their judgement as a result of the contextual information revealed to them. One expert gave the same, correct decision as before.
What methods in forensic science are vulnerable to cognitive bias ?
-visual observation with the human eye
-fingerprint analysis
-forensic anthropology
-hair and fibre analysis
-blood pattern analysis
-fire investigation
When do biases become problematic ?
when they narrow down our interpretations too fast, and close off alternative interpretations or solutions.
How can cognitive biases relate to one’s scientific training ?
By trusting an analytical approach because everyone else does it, even if the underlying scientific rationale or evidence base is weak.
What was the Casey report ?
Baroness Casey was commissioned to write a detailed report on the current state of the Metropolitan Police in 2023. This was primarily in response to the murder of Sarah Everard by a serving police officer. Her 363-page report concluded that it was ‘institutionally’ racist, misogynistic and homophobic.
What is the IOPC ?
Independent office for police conduct
Why did the IOPC dismiss 6 police officers in 2022 ?
For misconduct of sharing offensive messages and failing to challenge, report or condemn offensive views when they were found to share over 6000 messages in a WhatsApp group
What strategies are there to overcome bias ?
-blinding
-fillers
-Linear sequential unmasking
-case manager model
-peer review/blind verification
-experts’ acknowledgement of their potential for bias (or confronted with evidence of their own bias)
-education and training in cognitive bias
What is blinding ?
Giving no contextual information
What are fillers ?
Providing irrelevant evidence
What are the different types of guns?
-Self loading Pistol
- revolver
-Shotgun
-Rifle
What is the difference between rimfire and centerfire?
Rimfire refers to a firearm cartridge that has its priming compound located in a ‘rim’ around the base of the cartridge casing. Centerfire cartridges have an external pocket in the base where the primer is inserted.
What type of gun is a GFL 9mm Luger for?
Pistol
What type of gun is a Magtech .88 special-short for?
Revolver
What is the difference in ammunition for pistols and revolvers?
Pistol cartridges have a groove at the base that allows it to be ejected easily. Revolver cartridges have a larger base so that they are held in the cylinder.
What is the most common gauge for a shotgun?
12-gauge
What does calibre mean ?
It’s a unit of measure indicating the diameter of a gun barrel and the diameter of the gun’s ammunition
What is the bore?
The interior of the barrel of a firearm
What is the cartridge case?
It houses the bullet, primer and propellant
What is the primer?
The gun’s firing pin strikes the base of the cartridge and friction the cause ignition of the percussion primer
What is the propellant?
Chemicals that burn to create high pressure that forces projectile along barrel
After the primer has ignited the propellant what happens to the bullet?
hot gas is produced which expels the bullet
What is gun shot residue?
Any particle/ residue from the primer and propellant that are deposited on surfaces close to the gun
Why is primer residue more useful than propellant residue?
The chemical structure isn’t found in the general environment
What are the primary ways of acquiring gun shot residue?
-firing a gun
-Standing close to a gun when its fired
What are the secondary ways of acquiring gun shot residue ?
-handing a recently fired gun or spent cartridge case
-physical contact with someone who is contaminated
How much GSR is transferred each time it comes into contact with someone?
10%
How far does gunshot residue from a handgun travel ?
3m
What does primer gunshot residue contain?
Lead, barium, antimony and often other elements
How is primer GSR analyzed?
SEM- highly magnified images and chemical analysis
What does it mean for primer GSR to be highly characteristic ?
That it’s not produced by anything else other than guns/ firearms origin
What are advantages of primer GSR?
-recovered from surfaces using adhesive tapes
-Does not chemically degrade
What is the composition of primers?
-explosive
-oxidizer
-sensitizer
-frictionator
-fuel
-binders
What is an oxidizer?
Produces oxygen to enable combustion
What is a sensitizer?
Added to ammunition primers to make them more sensitive
What is a frictonator?
Substance that increases the sensitivity of the primer mixture to reduce the chance of misfire
What is the primer composition of sinoxyd ?
Lead Styphnate -explosive
Barium Nitrate- oxidizer
Lead Dioxide- oxidizer
Tetracene- sensitizer
Antimony Sulphide-fuel/frictionator
Calcium Silicide- fuel/frictionator
How long does GSR stay on bags, windows and vehicles ?
Depends on circumstances and cleaning
How long does GSR stay on clothing ?
Discarded clothing and pockets can be indefinite but clothing that is worn continuously up to 24 hours
How long does GSR stay on hands, face and hair ?
Hands- up to 4 hours
Face - up to 6 hours
Hair- up to 12 hours
What are types 1-3 of GSR ?
Type 1 - Lead, barium and antimony.
Type 2 - Lead, barium, antimony and aluminium.
Type 3 - Lead, barium, antimony and tin.
How is the calibre of a 20-gauge shotgun defined ?
The diameter of a solid sphere of lead weighing 1/20th of a pound
What are the different methods of detecting GSR ?
Bulk methods - colour tests
SEM
Why are bulk methods unreliable ?
The elements are common in the environment and doesn’t tell you whether the elements are in one particle
Why is SEM a better method of detection ?
-Analyses individual particles
-Distinguishes between different primers
-tells if the elements are in one particle
Why is GSR often round ?
Formed under high pressure
How are samples of GSR taken ?
-adhesive tapes mounted on aluminum stubs and carbon coated
-Now pre-prepared circular stubs more common
What level of GSR is considered very high ?
> 50 particles
Why are armed police officers likely to have GSR on their hands and clothing ?
As they carry firearms so they more likely to have high levels of GSR on them if they’ve recently fired their gun.
Why can armed police officers potentially ruin the evidence of a case ?
If the residue is the same as crime ammunition it can be impossible to determine the source
How must specimens in a SEM be ?
In a vacuum
What is the primary electron in SEM ?
Beam electron
What is the secondary electron in SEM ?
An electron from an atom in the sample knocked away by the primary electron
What are backscattered electrons in SEM ?
A primary electron deflected back by the nucleus of an atom in the sample
-The bigger the nucleus, the more backscattered electrons
How can you tell if a particle isn’t GSR ?
- There are no known primers
-no rounded shape
-presence of other elements
How does an SEM work ?
- The beam electron knocks an electron out of an atom in the sample
-An electron from a higher energy level in the sample atom drops to fill the gap
-by conservation of energy an X-ray is emitted with the same energy as the drop the electron in the atom made
What is the purpose of drug use Missuse Act (1971)
-means for control of all drugs
-grade penalties for misusing drugs
-brings new substances under control
-restricts prescription of drugs
-Established ACMD
What are the different classes of drug ?
A,B,C
What is the highest class of drug ?
Class A
What drugs come under class A ?
Cocaine and crack, ecstasy, heroin, LSD, methadone, methamphetamine and magic mushrooms
Which class A drug might be prescribed?
Methadone is prescribed to heroin addicts
What drugs are in class B?
Medical use: amphetamine, barbiturates, codeine, ketamine
recreational: spice, cannabis, mephedrone, methylone and methedrone, MDPV
What drugs are in class C?
Anabolic steroids, minor tranquilizers or benzodiazepines, GBL and GHB, Khat and BZP
How is possession of drugs divided ?
-possession for individual use
-possession with intent to supply
How is possession for individual use determined ?
Weight
How is the possession of drugs usually prosecuted ?
Usually prosecuted with another crime
What is the offence range for category 1(class A) ?
Maximum: 7 years
Range: fine- 51 weeks custody
What is the offence range for category 2 (class B) ?
maximum: 5 years
Range: Discharge-26 weeks custody
What is the offence range for category 3 (class C) ?
Maximum: 2 years
Range: discharge- community order
What is the offence range for possession with the intent to supply for Class A ?
Maximum: life
Range: community order- 16 years custody
What is the offence range for possession with the intent to supply for Class B ?
Maximum: 14 years
Range: fine- 10 years custody
Who would get a fine for possession of drugs with intent to supply of class B ?
Street level dealers
What is the offence range for possession with the intent to supply for Class C?
maximum: 14 years
Range: fine- 8 years custody
What is the first step in determining sentencing for possession with intent to supply ?
Determining the offence category
How does the court determine the offence category ?
Determine the offender’s culpability and harm caused
how does the court assess culpability ?
Weight up all the factors of the case to determine role and balance the characteristics to make a fair assessment
How does the court assess harm ?
Weight of the product. Purity isn’t taken into account
What is a leading role ?
- directing/ organizing on a commercial scale
-link to others in a chain
-close link to original source
-expectation of substantial financial gain
-uses business as a cover
-abuses a position of trust or responsibility
What business is typically used as a cover for drug dealing ?
Car dealership
What is a significant role ?
-operational/management function
-involves others by pressure, intimidation or reward
-motivated by financial gain
Some awareness and understanding of scale of operation
What is a lesser role ?
-perform a limited function
-engaged by pressure
-involved through exploitation
-no influence
-very little awareness
-absence of financial gain
What is county lines ?
using vulnerable people (children) to smuggle drugs across county borders
What is the weight of drugs in category 1 ?
Heroin/cocaine- 5kg
Ecstasy- 10,000 tablets
LSD- 250,000 squares
Amphetamines- 20kg
Cannabis-200kg
Ketamine-5kg
What is the weight of drugs in category 2?
Heroin/cocaine- 1kg
Ecstasy- 2,000 tablets
LSD- 25,000 squares
Amphetamines- 4kg
Cannabis-40kg
Ketamine-1kg
What is the weight of drugs in category 3?
Heroin/cocaine- 150g
Ecstasy- 300 tablets
LSD- 2500 tablets
Amphetamines- 750g
Cannabis- 6kg
Ketamine-150g
What is the weight of drugs in category 4?
Heroin/cocaine- 5g
Ecstasy- 20 tablets
LSD- 170 squares
Amphetamines- 20g
Cannabis-100g
Ketamine-5g
Why is the Uk an attractive market for drug dealing ?
Due to high street price, diverse ethnicity and major transport hubs
What were the NCA drug seizures in 2016 ?
69.8 tonnes of cocaine
4.5 tonnes of heroin
123.1 tonnes of cannabis
How much of the UK drug trade does the 2016 seizures represent ?
<2%
Where do illicit drugs in the Uk originate ?
- grown overseas and imported- cocaine, cannabis resin and heroin
-grown within the UK- cannabis (75%)
-synthesized within the UK or Europe- MDMA
What are the major trafficking routes into the UK for illicit drugs ?
- Cannabis: North Africa via Spain
- Heroin: typically originates from the golden crescent and enters via turkey
- Cocaine- originates in S.America and enters through Africa and Spain
Where does the majority of heroin in the UK originate ?
90% originates from the golden crescent
Where does the remainder of heroin come from?
SE Asia the golden triangle
What is the difference between afghan heroin and SE Asia heroin ?
SE Asia- white, high purity (80%), contains diamorphine hydrochloride and a few other opium alkaloids
SW Asia- cruder product, brown, 50% purity, contains diamorphine base and significant amount of noscapine
Where does cocaine originate ?
central and Northern America
How is cocaine transported ?
Body packers
What are body packers ?
The consumption of drugs for transportation within the body
What is used to transport the drugs in body packing ?
Drugs may be placed in condoms or in packets enclosed by several layers of polyethylene or latex
Why do body packers take anti-motility drugs ?
Reduce bowel movement
What is the risk of body packing ?
the total amount for drugs involved resents a super lethal dose, rupture of one or more packets is a risk and can result in abrupt toxicity or overdose
Who is often used as body packers ?
Pregnant women as it’s illegal to subject them to X-Rays due to radioactivity
What type of cannabis do cases usually involve ?
Skunk cannabis
What yield do plants submitted from grow rooms typically have ?
45g or 90g per plant
What is the sequence for testing illicit drugs ?
-drug sample
-physical description
-sampling- typically 10%
-presumptive tests (colour change test)
-quantification
-expert report
What are the two different types of analysis carried out ?
Presumptive and confirmatory
What are the different confirmatory tests ?
-UV
-IR
-GC-MS
When is purity testes ?
On request or if it is a large consignment of drugs
What is the marquis test ?
capable of detecting most opium based drugs such as heroin, morphine and MDMA
What does the marquis test consist of ?
A mixture of formaldehyde and sulphuric acid
How does the marquis test detect opiates ?
A violet colour is obtained from the formation of an oxonium ion after dimerizarion of 2 molecules of formaldehyde and opiate
how does the marquis test detect MDMA ?
Orange colour is obtained from the formation of a central carbonic
What is the cobalt thiocyanate test used for ?
Cocaine
What colour does the cobalt thiocyanate test turn in the presence of cocaine ?
Blue
What does the cobalt thiocyanate test contain ?
CT, glycerin, HCL and chloroform
What does the Duquenois-Levine test for ?
Cannabis
What does the Duquenois-Levine test contain ?
Vanillin, acetaldehyde, HCL and ethanol
What colour does Duquenois-Levine test turn in the presence of cannabis ?
Purple
how does thin layer chromatography work ?
-A series of drugs (known) are spotted on the plate and is stood in a shallow layer of solvent in a covered beaker.
-the atmosphere in the beaker is saturated with a solvent vapour
-The solvent will rise up through the plate and separate drugs into its multiple spots at different locations on the plate
How is Rf calculated ?
Distance travelled by component/ distance travelled by solvent
How does IR work ?
Obtained by measuring the interaction of IR radiation with a drug structure. A molecules absorbance of IR is unique to its structure so each molecule can give its own unique IR spectrum.
What is the fingerprint region ?
the most complex IR spectrum, this is the region with the most structural selectivity and thus it is this region that is ued separate individual drugs from the same classes
What is the issue with a spike in purity ?
more likely to Overdose
Why is Benzocaine the most common cutting agent ?
cocaine was originally a dental anesthetic so makes it appear more pure to some
What are the major factors of growing cannabis plants ?
-sex of plant
-light exposure
-flowering yield
-natural selection
How have Yorkshire produced higher yield plants ?
-better seeds
-better light
-better agricultural knowledge
how many hours of light does a cannabis plant need in the vegetative phase ?
24 hours
how many hours of light does a cannabis plant need in the flowering phase ?
12 hours produces the highest yield
What is a poison ?
Doris sola facit venenum= ‘only the dose makes a poison’
Poison refers to how lethal the drug is
What are different types of poisoning cases ?
-self poisoning
-acute poisoning
-fatal poisoning
-munchausen syndrome/ munchausen syndrome by proxy
-chronic/ acute on chronic substance abuse
-occupational/ environmental
-mediated (poisoning scares)
What is Münchausen syndrome/ Münchausen syndrome by proxy ?
Münchausen syndrome- making yourself sick for attention
Münchausen syndrome by proxy- inflicting harm on others to look after them for attention/ gratification
What is LD50 ?
Refers to the dose of a substance that kills half the test population, usually within 4 house. Typically expressed mg of substance per kg of body weight
How many tablets would be needed to kill someone that weighs 70kg if the LD50 of paracetamol is 2000mg/Kg ?
70x 2000= 140,000
140,000/500mg tablet= 280 tables
What is considered extreme toxicity ?
<1 mg/kg
What are the symptoms of caustic poison (lye) ?
Characteristic burns around the lips and mouth of victim
What are the physical symptoms of carbon monoxide poisoning ?
Red or pink patches on the chest and thigh, usually bright red lividity
What are the symptoms of acid poisoning ?
Sulfuric acid= black vomit
Hydrochloride acid= greenish-brown vomit
Nitric acid= yellow vomit
What are the symptoms of phosphorus poisoning ?
Coffee-brown vomit, onion or garlic odor
What are the symptoms of cyanide poisoning ?
Burnt almond odor
What are the symptoms of metal poisonings (arsenic, mercury) ?
Extreme diarrhea
What are the symptoms of methyl or isopropyl alcohol poisoning ?
Nausea and vomining, unconsciousness, possibly blindness
What is the most common form of poisoning in the UK ?
Carbon monoxide
How does carbon monoxide affect the body ?
Binds to haemoglobin with a 230x greater affinity than O2
-causes competition between CO and O2 for binding sites
-as CO binds with greater affinity and lower concentration is needed to saturate haemoglobin
-this causes tissues to become starved of oxygen leading to anaerobic respiration
What is the prevalence of CO poisoning ?
-decline in early 60s due to replacement of coal
-gas with natural gas that has lower CO content
-increase in males from mid 80s due to suicides
-introduction of catalytic converters caused decline in 90s
What are diagnostic features of CO poisoning ?
-more than one person in house is affected
-symptoms related to cooking
-symptoms worse in winter (heating in greater use)
-symptoms ameliorate on holiday but recur on return
-some groups (elderly, babies, pregnant women) more susceptible to CO toxicity
-symptoms similar to influenza
What is cyanide ?
A rapidly acting, highly toxic chemical that may come as a gas or crystal salt form
What is cyanide in its gaseous form ?
Hydrogen cyanide or cyanogen chloride
What is cyanide in its crystal form ?
Sodium/ potassium cyanide
How does cyanide affect the body ?
- binds to the same heme group as O2 blocking it from binding
-O2 is not reduced, interrupting ATP production causing death
What is the main toxicity following paracetamol poisoning ?
-acute liver injury which results from the formation of a toxic metabolite of paracetamol (NAPQI)
What happens when a therapeutic dose of paracetamol is taken ?
- paracetamol is metabolized into 2 major non-toxic metabolites- sulphate and glucuronide conjugates- which accounted for 30% and 55% of paracetamol metabolism
-NAPQI is formed in small amounts and is detoxified by irreversible glutathione-dependent conjugation reactions to two non-toxic metabolites
What is NAPQI ?
It’s a highly toxic metabolite formed by cytochrome P450 2E1 and is responsible for the hepatocellular injury that occurs with paracetamol toxicity
What happens in paracetamol overdose ?
The increased formation of NAPQI depletes glutathione and binds to critical cellular proteins of the liver resulting in hepatic cell death
What is warfarin ?
Used as an oral anticoagulant to minimize the risk of blood clotting in the veins of patients
Why is warfarin dosage closely monitored ?
to ensure that the INR does not rise above 2-3 because if it does the patient risks a bleed of the brain
What else can be used to determine drug intake ?
Hair
How should hair samples be collected ?
- hair should ideally be taken from the posterior vertex region of the head
-two specimens each of approximately the e=thickness of a pencil should be taken
-the hair sample should be tied in some fashion
-cut as close to the scalp as possible
-samples should be labeled in such a fashion that it is easy to identify the proximal and distal ends of the hair
-should be stored dry at room temperature
What are issues with hair testing ?
-the rate of growth of hair is variable
-time for the hair to emerge from the skin is variable
-how close the hair has actually been cut to the scalp
-has the hair been cut at an angle ?
-drugs can be washed out of hair over time
-contamination (sebum, sweat, environment, hair treatment)
What is the average rate of hair growth used ?
1cm/month
What is haloperidol?
neuroleptic antipsychotic that is used for the treatment of acute and chronic psychotic states, anxiety, paranoid delusions and hallucinatory psychoses
What kind of cases might require chemical analysis of glass evidence ?
-burglary
-car accidents
-assault
Why is the location of glass relevant ?
The location of glass is dependent on what is analysed/ evidential value
How is glass recovered from clothing/ shoes ?
-seal pockets/ trousers turn ups
-recover hairs/ fibres by lightly taping
-shake item/brush onto brown paper
-check pockets and turnups last
How is glass and fibres recovered from hair ?
Combing
How is glass and fibres taken from other surfaces ?
Tweezers
What controls are taken from glass recovery ?
-blank sample
-reference sample at crime scene is taken from the frame not from the glass on the floor
When would a forensic scientist analysis glass ?
-SOCOs will recover glass or size items with glass on it.
-volume crimes- don’t usually examine glass because a suspect is not located quickly enough
-serious crimes-more likely to analyse glass evidence
What is the evidential value of glass in hair combing ?
Highest evidential value
What is the evidential value of glass embedded in soles of footwear ?
Lowest evidential value
What is float glass ?
-very common (windows)
-smashes into mixed sized fragments with sharp edges
-edges can tell us how fresh the smash was
What is tampered glass ?
-common (motor vehicles)
-safety glass
-hard to smash
-forms cubes
-tends to clump together
-edges indicate thermal or physical stress and impact
What is laminated glass ?
-2+ panes joined by plastic (PVB bond)
-common (windscreen glass)
-less common (bullet resistant, smart glass)
-sticks together
-safety
What is wired glass ?
-less common (fire doors)
-mesh through the pane
-tends to be indoors (rusting)
How does glass smash ?
Backwards fragmentation
What is a radial crack ?
Radiate in Amy directions away from the point of fracture
What is a concentric crack ?
Imperfect circle around the point of fracture
What are the different types of analysis for glass ?
-chemical
-refractive index
-mechanical fit
What is chemical analysis for glass ?
Identifies oxides in colouring and impurities in constituent parts used in manufacture
What is refractive index analysis for glass ?
Light refraction as it passes through glass, measured in heated oil. The RI changes as it’s heated, and when the sample disappears the RI value is known
What is mechanical fit for glass ?
Large fragments might stick together
Conchoidal stress marks
What equipment is used to analyse glass ?
-GRIM
-X-Ray fluorescence
-Scanning electron microscope
-surface examination
-annealing
What is GRIM analysis ?
Measures optical properties of glass
-tiny fragments <0.5 mm
What is X-Ray fluorescence analysis ?
Elemental composition of glass
What kind of cases might require chemical analysis of fibre evidence ?
-hit and run
-car crash/ accident
-sexual assault
-burglary
Where might you find samples of fibres ?
Everywhere
How are fibres recovered from clothing ?
-tape lifting
-plastic tweezers
-vacuuming
-shaking
-brushing
-place in paper bag
What are the different types of fibres ?
-natural and synthetic/man-made
-further classified: animal, vegetal or mineral
What are examples of natural fibres ?
Vegetable: cotton, hemp
Mineral: asbestos
Animal: wool, silk
What are examples of man made fibres ?
Natural polymer: acetate, viscose
Synthetic: polyester
Inorganic: carbon, glass
What does cotton look like etc ?
- strong, tough and flexible
-absorbs moisture
-doesn’t retain shape
-length and degree of twist differed based on type of cotton
-if ignited burns with steady flame
-smells like burning leaves
What does linen look like etc ?
-individual plant fibres are longer
-takes longer to ignite
-if burning can be extinguished by blowing like a candle
What does silk look like etc ?
-burns easily but not as steadily as Cotten/ linen
-smells like burning hair
-not as easy to extinguish
What does wool look like etc ?
-from sheep’s, goat
-individual fibres are shorter than silk
-diameter of fibres is relevant
0fineness indicates usage-clothing vs carpet
-harder to ignite with a steady flame but difficult to keep burning
-smells like burnt hair
What does acrylic look like etc ?
-made from natural gas and petroleum
-retains shape; wool like
-resistant to moths, sunlight and oil
-burns readily due to contents and air filled pockets
-will ignite fast and will continue burning until extinguished
-smells acrid or harsh
What does nylon look like etc ?
-made from petroleum
-exceptionally strong and abrasion resistant
-damage resistant to oils and many chemical
-low in moisture absorbency
-melts and burns fast if flame remains on melted fabric
-smells like burning plastic
What does polyester look like etc ?
-made from coal, air, water and petroleum products
-strong-resistant to stretching and shrinking
-resistant to most chemicals
-quick drying
-wrinkle resistant
-melts and burns at the same time
-dripping ash Bon’s with any surface it encounters
-smells ‘sweetish’
What do synthetic fibres tell us about?
-blends- two or more fibres
-should take characteristics of each fibre
-burning test can be used but fabric content will be an assumption
What identification techniques are used for fibres ?
-primary examination
-chemical examination
What is the primary examination for fibres ?
-visual - colour, location, amount
-microscope - comparison
-birefringence
What is the chemical examination for fibres ?
Involves the extraction of dye and identifying and characterising the chemical structure
What equipment is used to analyse fibres ?
-SEM
-Raman spectroscopy
-IR spectroscopy
-UV vis spectroscopy
What kind of cases might require a chemical analysis of paint evidence ?
-hit and run
-car accident/ crash
-break in
Why don’t SOCOs use tape to lift paint samples ?
Paint has multiple layers so the tape might remove a layer
How is paint recovered from clothing ?
-plastic tweezers
-shaking
-brushing
-place in paper bag
How is paint removed from other surfaces ?
-tweezers
-sharp edged knife
What is the chemical examination of paint ?
Side by side comparison under Low power stereo microscope for colour, surface texture and colour layer sequence
What is colour layer sequence ?
-trying to match the layer number and sequence of colour as it the sample will be made up of diffferent layers (base coat, binder, primer and topcoat )
What is the second part of the chemical analysis of paint samples ?
Analysing individual layers
