forensics Flashcards
what does a forensic scientist do
give impartial evidence in relation to the law by carrying out a variety of analytical measurements which are used to discriminate between individuals/groups
what does the extent of forensic analysis carried out depend on
the scientists experience
time pressures
costs
when is forensic science required
when a crime has been committed and you are trying to finds the responsible person
need to determine whether death was by natural causes or not
when and where did forensics begin
in the 6th century with use of finger prints in china
what are the 4 main areas for forensic science and give examples of work carried out in each
biology - biological sample testing
chemistry - firearm residues, object analysis
toxicology - drugs and alcohol
documents - anything with writing - inceptive analysis
what are the 7 types of forensic scientist
pathologist entomologist dentist psychologist scene of crime officer archaeologist anthropologist
what are the 2 basic principles in forensic science
locard’s principle
physical fit
what is locard’s principle
every contact leaves a trace - either leave something behind or take something away
what is physical fit
physical fit can prove beyond reasonable doubt the connection between a crime scene and a suspect
evidence fit together
what is the chain of custody/evidence
preserve the scene
search for material of evidential value
all evidence must be packaged and labelled correctly
safe storage and transmission to the lab
evidence needs to be handled properly
can be acquitted if evidence isn’t collected properly
what is trace evidence
provides a link between suspect and victim/locus
very small amounts of material
what are the 2 types of trace evidence
reactive trace
inceptive trace
what is reactive trace
know something about the suspect and looking for links
e.g. know the suspect was wearing a green hat, look for fibres on victim
what is inceptive trace
don’t know anything about the suspect but find green fibres on victim, find link to suspect
what are some of the difficulties looking for trace material
the amount of material often limited
need to know where to look
need to estimate the evidential value of the material
give examples of how we recover evidence
shaking brushing taping vacuuming swabbing hand picking extracting pipette/swab
how can we analyse glass and what do we get from it
colour and thickness
physical analysis - refractive index - the further away from the average (1.5) the rarer it is
chemical analysis - scanning electron microscope and energy dispersive X ray analysis
information from crater shaped holes indicate direction of impact
what is a fibre
any long thin flexible solid with a high length to transverse cross section area ratio and can be man made or natural
what are methods of fibre analysis
microscopy
tapings
TLC
IR spec
what are the components of hair
medulla (sometimes absent), cortex (made of cortical cells) and cuticle (made of scale cells)
how can we use hair for classification
human or animal hair testing what part of the body is it from can we determine race is it dyed - artificial alteration damage - are roots present
why can hair have limited evidential value
if the roots are absent there is not much we can infer from it
if the roots are present we can determine blood groups and possibly DNA profiles
how can hairs be useful for toxicology
drugs in hairs can affect length - we can determine the extent of drug use and when it stopped if it did
how can we characterise blood
human or animal what type of animal if human blood what type sex race
what are some points to note about preliminary testing for drugs
not entirely specific
false reactions
rbcs and platelets have no DNA
what are the 3 tests we can do for bloods
LMG
phenolphthalein
luminol
what is the luminol test
luminol + hydrogen peroxide –> 3 aminophthalate (light given off)
what is the LMG test
LMG + hydrogen peroxide –> oxidised LMG (green)
what is the phenolphthalein test
phenolphthalein + hydrogen peroxide –> phenolphthalein oxidised (red)
what preliminary testing can we use for semen
microscopy
acid phosphatase
p30
DNA profiling - semen is a good source of DNA but seminal fluid contains no DNA unless it contains skin cells
what preliminary testing can we use for saliva
starch/iodine
salivary amylase
saliva may contain bacterial/cheek cells
what is the purpose of blood pattern analysis
to provide information regarding the sequence of events: the position of the victim and evidence of struggle
provide evidence to corroborate or refute statements made by those involved
what are the 3 types of blood pattern
passive
transfer
projected/active
what is blood stain pattern analysis
examination of shapes, location and distribution patterns of blood stains in order to provide an interpretation of the physical events which gave rise to the origin
what is a passive pattern
due to gravity: drops drips pools clots shape effected by target surface texture
what is a transfer pattern
wet bloody surface on contact with another surface produces a pattern
- contact
- swipe/smear
- wipe
- smudge
what is a projected pattern
arterial spurt/gush
cast of stains
can infer impact
point of convergence
what factors do we need to consider when looking at the significance of trace evidence
- extent of comparison
- rarity of trace material
- expectations
- combination of evidence
- alternative innocent sources
- contamination
what is alcohol
ethanol is clear, colourless and miscible with water
what is alcohol produced by
fermentation from grapes and cereal grains
what are the steps in absorption and distribution of alcohol
mouth
GI tract
circulatory system –> brain, kidneys, lungs and liver
what % of alcohol is absorbed in the stomach
20%
what % of alcohol is absorbed in the small intestine
80%
what factor can effect the rate of alcohol absorption
- quantity of alcohol consumed
- concentration of alcohol
- contact time in GIT
- food - food intake delays the transfer to the small intestine which in turn delays absorption
- stomach emptying - changes how long it takes to move to the small intestine
the distribution of alcohol is rapid/slow
rapid
alcohol is distributed to all organs and body compartments but how are the proportions decided
by the organ/compartments water concentration - the higher the water content the more alcohol can be absorbed because alcohol is miscible with water
most organs and fluids are in a constant equilibrium with ………..
blood
list the affects associated with different alcohol levels
mg/100ml under 50 - not obvious, talkative 50-100 - slurred speech, coordination loss 100-150 - loss of gait, possible nausea 150-200 - nausea, non- cooperative 200-300 - probable coma 300-400 - coma, impaired respiration 400+ - death may ensue from respiratory paralysis
what % of the alcohol consumed is metabolised
90%
what are primary and secondary alcohols oxidised to
aldehydes then carbon dioxide and water
what is the main enzyme involved in alcohol metabolism
alcohol dehydrogenase
what is the reduction in blood alcohol content on average per hour
18mg/100ml/hr
what coenzymes needs to be present for alcohol metabolism
NAD
what is the toxic metabolite produced in alcohol metabolism
acetaldehyde - what causes hangovers
what is acetaldehyde converted to
acetate by aldehyde dehydrogenase
what is acetate eventually converted to
carbon dioxide and water
what is ADH
alcohol dehydrogenase
what are the differences between the different isotypes of ADH
different structural, physical and chemical properties
there are fast and slow metabolisers
different Km and Vmax
what is pharmacokinetics
how the body metabolises and copes with drugs that are present
what is zero order kinetics
cleared at a constant rate regardless of concentration
what order of kinetics is ethanol clearance from the body
zero order - cleared at a constant rate regardless of concentration
what does the pharmacokinetics or alcohol depend on
liver size and body mass
large liver = more enzymes = more alcohol metabolism
larger body = greater alcohol distribution = less effect
what is the cytochrome p450 pathway
- is an oxidative pathway of alcohol metabolism involving a microsomal enzyme oxidising system (MEOS)
- the pathway contains a family of enzymes containing heme as a cofactor that function as monooxygenases- catalysis of oxidative reactions
- the enzymes are predominantly present in the microsomes and contribute to alcohol oxidation in the liver
- within the system you use up NADPH which affects other pathways
- the pathway is most prevalent in chronic alcoholics because alcohol concentration is regularly high
- problem - produces free radical which damage tissue
summarise sections of the road traffic act 1988
- driving a motor vehicle whilst unfit through drink or drugs
- being in charge of a motor vehicle whilst unfit through drink or drugs
- driving a motor vehicle after consuming so much alcohol that the proportion in breath, blood or urine exceeds prescribed limits
what are the legal limits of alcohol in Scotland
blood - 50mg/100ml
breath - 22ug/100ml
urine - 65mg/100ml
compare Scotland’s legal driving alcohol limits with the rest of the UK
they are much lower
what physical samples can we use to measure alcohol content
breath urine perspiration saliva blood
what is the best measurement of alcohol concentration and why
BAC because it is equivalent to the conc in the brain
what are the 3 most common methods of measuring alcohol content
blood - most accurate - rapid equilibration across the blood brain barrier
urine - provides mean value over the period of excretion
breath - in equilibrium with BAC but in very small concs
what are the equations for converting between blood, breath and urine alcohol conc
BAC x 1.3 = urine
(mg) (mg)
BAC/2300 = breath
(mg) (ug)
ADH in the presence of its coenzyme, …………….., oxidises alcohol
NAD+
how can the reduction of NAD+ during alcohol metabolism be measured
calorimetrically
spectrophotometrically
how do electrochemical fuel cell breathalysers work
electric current passes through and the conc of alcohol determines the strength of the current
how do IR optical sensor breathalysers work
light is fired at a sample and the concentration of alcohol affects the light absorbed
how do dual sensor breathalyser work
both chemical and IR
apart from using the 3 types of breathalysers how else can we measure alcohol content of a sample
gas chromatography
what is the equation for calculating BAC
Cmax - (t x elimination rate) where the average elimination rate is 18 the minimum is 9 and the maximum is 27 t is the number of hours Cmax is the maximum alcohol conc
heavy drinkers tend to have increased/decreased rate of alcohol metabolism from the average value
increased
why are heavy drinkers faster at metabolising alcohol
because they have alcohol dehydrogenase metabolism and the p450 system so they metabolise alcohol more quickly
when given limit and amount of alcohol in sample how do we figure out when the person will be able to drive
we find out how much the conc needs to decrease by then divide by the average elimination rate
describe the auto brewery/gut fermentation system
if certain yeast are present in the gut at high conc which produces ethanol - would have alcohol in the blood even without having a drink
what is forensic toxicology
study of the effect of alcohol, drugs or poisons with application to the law
e.g. post mortem toxicology, human performance, drug testing in the workplace/sports
what is the Paracelsus’s statement about the Paracelsus’s third defence meaning
what is there that is not poison, all things are poison and nothing without poison - solely the does determines that a thing is not poison i.e. too much water can cause death
what is the problem with babies being given food that their parents eat
there is too much slat in the food and results in kidney failure in the babies
what is a controlled substance
any drug subject to misuse under the drugs act 1971
give examples of controlled substances
heroin, LSD, solvents - can cause liver kidney and brain damage if used too much, cannabis
what are some reasons for poisoning
suicide
accident - too pure, not cut/mixed properly
industrial - poisoning in the workplace
homicide - murder
iatrogenic - murder by healthcare professional
list some Class A drugs
major natural and synthetic opiates cocaine LSD injectable amphetamines cannabinol magic mushrooms ecstasy
name some class B drugs
oral amphetamines
cannabis plant material and resin
codeine
certain barbiturates
name some class C drugs
benzodiazepines
methaqualone
gama hydroxybutyrate
ketamine
what are the 3 drug type categories and give examples of each
stimulants - stimulate/activate brain - cocaine
depressants - inhibit brain activity - alcohol, heroin
hallucinogens - induce alterations in perception and mood - LSD, ecstasy
what type of information can we get from drug analysis
qualitative/quantitative
bulk/trace
chronic/acute
what are methods of drug analysis
presumptive tests TLC column chromatography HPLC gas chromatography and mass spec immunoassay spectroscopy
what human sample can we use to infer if drugs are from the air or have been inside the body
hair
- drugs bind to melanin - weak bases (bind easily) - the more melanin the better the drug binds - darker haired people have more melanin
- if the drug has been added to the hair through ingestion or injection there is a pattern but if the drug has been smoked we don’t see a pattern
as well as finding the actual drug in a body sample how else can we finds the drug
by looking for it metabolites
which core drugs are tested for in the workplace and what samples do we take to test for them
cannabis cocaine amphetamines opiates testing: saliva, urine, hair
what is pharmacokinetics
what the body is doing to the drugs
the study of the absorption, distribution, metabolism and excretion processes over time
what is pharmacodynamics
what the drug is doing to the body
the study of the dose vs. pharmacological response
what is pharmacogenetics
the study of genetic influences on the absorption, distribution, metabolism and excretion processes - different people react differently to drugs
what does ADME stand for
absorption, distribution, metabolism and excretion
what factors affect toxicity of a drug
- dose response - how much - LD50 value
- sensitisation - may have an enhanced immune response to a drug the second time
- tolerance - when repeatedly exposed
- accumulation - the longer the half life the greater the accumulation
- bioavailability - proportion of the original does absorbed and the rate at which absorption takes place
what is the LD50 value
where you get half of the maximum response - it can increase if people build up tolerance
what is the general shape of a dose response curve
S
what drug category are amphetamines in
stimulant - they increase dopamine levels
how can amphetamines be taken
inhalation
injection
ingestion
snorting
what are the short term affects of amphetamines
increased wakefulness and physical activity decreased appetite faster breathing rapid/irregular heartbeat increased bp and body temp
what are the long term affects of amphetamines
HIV/AIDS - sharing needles
weight loss
severe dental problems - meth mouth
which category of drug is MDMA/ecstasy
hallucinogen/stimulant
what are the affects of MDMA
- increased activity of dopamine and norepinephrine - increased energy and heart rate/bp
- affects serotonin levels
- blurred vision
- nausea
- muscle cramping
how long do the effects of MDMA last
3-6 hours
what can high doses of MDMA affect
temp regulation
what medical profession is MDMA used in but why is it not used very often
psychotherapy but not used often due to all the side effects
how is cocaine made or extracted
by extraction from cocoa leaf
or by chemical synthesis
how can you take cocaine
snorting, injection, oral
what drug category does cocaine belong to
stimulant - increases the level of dopamine
what are the short term effects of cocaine
extreme happiness and energy mental alertness hypersensitivity to sight, sound and touch irritability paranoia
what are other affects of cocaine
constricted blood vessels dilated pupils nausea raised body temp, bp and heartbeat tremors and muscle twitches restlessness
what are the active ingredients of heroin
diamorphines and other opiates e.g. codeine
how is heroin administered
smoking or IV
what are the effects of heroin
analgesia dreamy euphoria sedation respiratory depression - can lead to death nausea vomiting cough suppression constipation
what is respiratory depression
when ventilation becomes inadequate for gas exchange causing increased conc of CO2 and respiratory acidosis
what category of drug is LSD and what is it made form
hallucinogen
made from lysergic acid
what are the affects of LSD
affects the action of glutamate and serotonin rapid emotional swings distortion of reality, rationality and communication raised blood pressure, heart rate;, body temp dizziness and insomnia loss of appetite dry mouth sweating numbness weakness tremors dilated pupils
how is LSD administered
microdots
how is cannabis administered
smoking, dabbing, food
how does the class of cannabis change
cannabis plant and resin - class B cannabis oil - Class A
what are the effects of cannabis
euphoria nausea hypotension bloodshot eyes poor coordination distortion munchies
how quickly does cannabis act
smoking - minutes
oral - 1 hour
is cannabis accepted for medical use in the UK
no - we are unsure of long term medical use effects
what are benzodiazepines
prescription drugs
how are benzodiazepines administered
oral, injection
what are the effects of benzodiazepines
depressants - reduce tension and anxiety
cause drowsiness
what is the date rape drug
flunitrazepam
what is blood grouping
a preliminary screen which defines a persons blood group in a quick and cheap manner allowing elimination of suspects from large samples
what are the antibodies on cells and the antigens in serum for each of the different blood types
type - antigen - antibodies A - A - Anti B B - B anti A AB - AB - neither anti A or anti B O - neither A or B - both anti A and anti B
what are the possible allele combinations for each of the blood types and their % distribution
O - O - 45%
A - AA, AO - 40%
B - BB, BO - 10%
AB - AB - 5%
what is a biological marker
a measurable indicator of some biological state or condition
we can carry out immunological procedures using ………….. to find our which antigens are present in sample
antibodies
what are secretors
they secrete ABH antigens of ABO blood group in other bodily fluids (saliva, semen, gastric juice etc)
other fluids have a very similar profile to the blood serum
secretors have a higher concentration of which antigens
A and B
what is the difference between secretors and non secretors
for secretors we can use other fluids to determine blood type but for non-secretors we have to use blood
what case was DNA profilin fist used for
Colin pitchfork
what are good sources of DNA in the body
wbc sperm cells hair with follicle vaginal fluid bones teeth
what are bad sources of DNA in the body
skin cells - better with new technology
urine
hair shaft - only mDNA
faeces
what is the same in identical twins
DNA and micro RNA expression
what are some marker types for autosomes
STRs
SNPs
SNPs don’t have the best discriminatory power so we are best to use STR
what are the markers for mitochondrial DNA
SNPs
what is RFLP
restriction fragment length polymorphism
- cuts up DNA using restriction enzymes
- there are STRs within the cut up sections and the lengths of repeats very among individuals
- a DNA sample is digested into fragments by one or more restriction enzymes and the resulting fragments are separated by gel electrophoresis
what are the limitations of RFLP
large amounts of DNA are required
requires undegraded material
what is the method of using PCR to amplify STRs
we use PCR then gel electrophoresis
why are STRs good for forensics
because the number of repeats of STR markers can be highly variable among individuals
why is a smaller STR better
PCR amplification of degraded DNA works better with smaller target product sites
because of the smaller size STR alleles they can also be separated form other chromosomal locations ensuring closely linked loci are not chosen
what are the benefits of PCR of STRs
STRs have lower mutation rates making them more stable and predictable
STRs with higher power of discrimination can be chosen for forensics
less DNA is required
we can use partially degraded material
what is used more often PCR or RFLP
PCR
how is PCR of STRs now automated
samples are tagged with fluorescence and put through a capillary gel which gives readings based on fluorescent tags
what is the difference between STRs and SNPs in terms of fluorescence tagging
SNPs are tagged with fluorescence bases
how many circular molecules of DNA does 1 mitochondria have
5-10 each with 37 genes
when is mtDNA useful in forensics
in mass disasters to link family members as it is passed from mother to children
discrimination is limited especially if individuals are maternally related
still effective when:
very small sample
badly degraded
describe Y chromosome testing
it uses amelogenin locus and/or STRs on the y chromosome
- amelogenin codes for enamel in teeth and in the X chromosome if 6bp shorter
- in testing, 2 peaks represents a males as there ar 2 different lengths of DNA present
- STRs on the y chromosome only appear in male samples and can be seen of autosomal and y chromosome profiles
useful for mixed gender samples - sexual assault
but low discriminatory power
what is the main DNA analysis and why
autosomal STR due to the high discriminatory power
when is autosomal SNNP analysis used
when sample size is too small for autosomal STRs
what is low copy number analysis
used when we have little DNA
what is familial searching
it is based on the principle that relatives will share features of their DNA profiles more than unrelated individuals
what is heteroplasmy
the presence of more than one type of DNA within an organisms
low level variation
mitochondrial DNA has a high/low mutation rate
low - it changes very little when passed maternally through families
what is DNA boost
computer programme which searches DNA profiles
the database creates all possible genotypes of a mixture with different STR length repeats
what are some applications of DNA profiling
familial searching cold cases - look at cases that were closed before DNA profiling was available linking/identifying families wildlife crime ethical issue
what is codis
US based system that uses 13 core STR loci
what is UK NDNAD
the system uses 11 loci in total including 10 STR loci and XY (amelogenin)
how do we calculate the probability of finding a DNA match on DNA database systems
number of times the event happened/ the number of times the event could have happened
what are the 3 possible categories of results when carrying out DNA profile comparisons
exclusion - non-match
inclusion - match
inconclusive
how do we work out probability for 2 allele locus
F(1, 1) = p^2
F(1, 2) = 2pq
what are the 2 possible errors that can occur in PCR STR amplification
backwards slippage
forward slippage
what is backward slippage
causes an insertion - an extra STR repeat is inserted
what is forward slippage
causes a deletion - an STR repeat is lost - very small bands (stutter products are produced due to this mechanism
what are the advantages and disadvantages of low copy number analysis
only need small amounts of DNA template
it has the same discriminatory power as routine DNA profiling
the process takes longer because a greater number of PCR cycles are required to get sufficient DNA quantities
what is a partial DNA profile and what can they be used for
they are DNA profiles that are not complete - this may be due to low quality DNA possibly due to degradation of the sample or insufficient quantity
they can be used for familial searching
we can look for similarities in the profile that are on the database
we can use low copy number analysis
how do we increase the probability of finding a match with a partial profile
we have to prioritise using specific parameters for example location and police intelligence
give an overview of the M3 murder
a group of men tried to steal a car and threw bricks from a bridge on the M3
the mixed profile from the brick matched that in the car by using low copy number DNA but they found no match on the database
familial search was carried out they found the suspect
what programme in particular has become very useful for cold cases
DNA boost
what was operation magnum
the first use of familial searching on NDNAD
several women were murdered and low copy number analysis found matches on their clothes
a familial search was carried out and the suspect was found
outline the shoe rapist incident
women were being raped by a man that was keeping their shoes
familial search used lead them to the sister of the rapist and they found him
outline the Romanovs case
tsar, wife and 5 kids executed
a grave was found and STR and mtDNA analysis found that 5 of the 9 skeletons were related
woman claimed to be Anastasia by had different mtDNA
what markers can we use for visual identification
hair, skin colour, eye colour, piercings, tattoos
in bosnia there are ~40 burial sites and blood and bone samples were taken and compared with relatives - what were the difficulties with this
whole families were killed - nothing to compare with
shallow graves - bodies dug up by animals and bones scattered
give an example of a mass disaster and false identification
tsunami in indian ocean - people were so distraught that they were wrongly identifying bodies as family members
what did the 9/11 disaster lead to
new extraction methods from bone
mini STRs - shorter area - easier analysis
use of SNPs
use of mtDNA
sadaam Hussein had body doubles, how did they identify him
by use of Y STR haplotypes
what is genetic diversity caused by
polymorphisms
how can we detect genetic diseases by RFLP and PCR
mutations can cause changes in the restriction sites and the size of fragments
give examples of genetic diseases that can be detected by RFLP or PCR
sickle cell anaemia
cystic fibrosis
give some examples of wildlife crime
crime towards rare animals can cause threat to species
we can trace crimes by looking at non human DNA profiles
animals can be victims of crime but animals can also cause damage to humans e.g. traffic accidents and flesh and bone damage
what is entomology
the study of insects
what are the areas of application of entomology in forensics
we use insects to infer the cause, time and details of death
- some insects inhabit remains
- some insects cause damage to structure
- some insects infest foods
what are some of the forensic associations of insects
found on corpses e.g. diptera
food spoilage e.g. butterflies
structural damage e.g. beetles
illegal trade in protected species e.g. butterflies
indication of neglect e.g. lice and fleas
cause of death e.g. wasps
why do lice leave the body when it dies
because they need the warmth
what is the post mortem interval
the interval between the time of death and the post-mortem exam and is often given as an estimate in a range
what methods can be used to determine PMI
Algor mortis livor mortis rigor mortis changes in eye fluid stomach and bone contents decomposition changes insect colonisation circumstantial evidence
what is Algor mortis
cooling of the body
what is livor mortis
hypostasis - gravity causes blood to sink
what is rigor mortis
stiffening of the body
how can we infer PMI from stomach and bowel contents
we might be able to so what someone has eaten - may lead us to a location
might indicate an allergy
might indicate when food was consumed
how can insect colonisation indicate PMI
successive colonisation can indicate time of death - what species are present indicates how long the body has been dead for
what is circumstantial evidence
evidence that requires inference to conclude facts e.g. finger prints at crime scene
how does the season affect entomology
season of death if one is outside can majorly impact the insects that will colonise and also affects the rate of decay
what is meant by insects colonising successively
they don’t all arrive at once - they arrive in stages - specific species prefer different levels of decay
how can we interpret changes in location after death using entomology
the insects found on a corpse may not be local to a particular area so this would indicate that the body was moved after death
give examples of how circumstances of death can affect insect colonisation
- was the body on the surface for a while then buried
- was the body in water if so what kind and in what season- aquatic insects
- toxicology - some insects eat flesh or blood - these insects can be analysed to check for drugs etc
development time of insects is ……………. dependent
temperature
give 7 reasons why insects are successful
1 - metamorphosis 2 - feeding strategies 3 - sophisticated behaviours 4 - small and difficult to catch 5 - chitin exoskeletons 6 - wings - can easily evade danger 7 - life cycles - intricate and efficient
what is metamorphosis and why does it improve success of insects
the process by which an animal physical develops after birth which involves changes in the body structure through cell growth and differentiation
metamorphosis is often accompanied by a change in nutrition source or behaviour which allows them to exploit other resources
why are feeding strategies of insects a contributor to their success
they have very specific feeding strategies
give examples of sophisticated behaviours of insect that improve their success
many insects use sensory neurons to attract them to other sites
why is chitin an advantage to insects
it is a hard coating which forms their exoskeleton and acts as part of their defence mechanisms
what do the insects do once they have exploited the nutrients from the corpse
they leave the corpse
how can insects be mistakenly associated with a crime
they may be caught in the clothing or be landed on but they are not actually feeding on the body, they are just in close proximity with it
how can invertebrates be the cause of death
some invertebrates are venomous
some people have allergies to insects
what are the 5 stages of entomological succession
- blowflies
- flesh flies
- burying/histerid beetle
- house flies
- dermestid beetles
what are the stages of corpse decomposition
- fresh - body starts cooling - autolysis - hypostasis and rigor mortis may begin
- bloat - discoloration, body swelling - fluid expelled form orifices - rapid decay dur to intense microbial and invertebrate activity - soft tissue decay
- putrefaction - loss of skin and soft tissue - deflation - decay by microbes and invertebrates slows down once soft tissue is removed and body dries out
- putrid dry remains - slow progress of decay - loss of uterus and prostate gland , tendons, cartilage, fingernails and hair - skeleton may become disarticulated what
what is an instar
an insect stage of development
what are the first organisms to arrive at a corpse
flies - blowflies, flesh flies, house flies
what are the stages of the blowfly life cycle
- adult female blowflies arrive within minutes to lay eggs on a corpse in wounds and natural openings
- in 24 hrs the eggs hatch into 1st stage maggots
- with feeding they moult to 2nd stage maggots
- with further feeding they moult to 3rd stage maggots
- with further feeding the maggots move away from the body to metamorphose and develop into flies
what is there an increased threat to used pathogens for
to release them maliciously or to cause distress
what environmental conditions can affect decomposition
cold, dry - slow decomp
warm, moist - fast decomp
are we able to work out the time of death by looking at microbes
not yet
how can microbes be used as identification tools
soil microbes - where has the body been
saliva microbes - what have we been eating
microbial infection
food poisoning - trying to find the source
what are the 6 types of evidence covered in this course that are collected from forensic examination
- time of death - can help look at alibies
- trace evidence - hair, fibres etc
- blood patterns - different types - can indicate trauma type
- DNA profiling - can connect evidence to suspects
- Entomology - insects and forensic use
- toxicology - drugs
what is a nomogram
we measure rectal temperature and ambient temperature and plot lines
- where the lines cross we draw a line through the central point and the crossing point
- we know the weight so we follow around the curve to get the estimated time of death
how can we calculate the number of hours since death using body temperature
98.4 - internal body temp/ 1.5
what are the indications of time of death form stiffness and warmth
warm not stiff <3hrs
warm stiff 3-8 hrs
cold stiff 8-36 hours
cold not stiff >36 hours
are insects more accurate for inferring longer or shorter times after death
longer
what factors can enhance the cooling of a body
small body low fat stretched out body dismembered serious blood loss no clothes wet clothes strong air currents low ambient temp body in cold water
what factors delay body cooling
large body high fat foetal position clothing insulative covering protection from draught warm ambient temp microclimate warm exposed to sun high humidity
what is pressure pallor
white mark where the pressure was on the corpse
outline the soham murders
hairs and fibres found on girls football shirts in bin and the evidence was linked back to the suspect due to finding the same fibres in his house
outline the jill dando case
BBC presenter shot at her door - polyester fibres and gun residue on her coat led investigators to the suspect
why are some clothing items not very discriminatory
if they are popular then they are not very discriminatory
outline the billie jo Jenkins case
they found an impact scatter at the scene and thought it was caused by trauma initially but it was actually caused by pulmonary emphysema - much debate between experts - required a lot of collaboration
describe the Harold shipman case
possibly committed 200 murders but will never be certain unless all bodies are exhumed and re-examined
he was found out through false entries - false signature
found high morphine content in victims bodies
