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Human Biosciences > Forensics > Flashcards

Forensics Flashcards

1
Q

Locard exchange principle?

A

Every contact leaves a trace

The ultimate limit is a single atom

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2
Q

First step in analysing a crime scene?

A

Alternate light source in the blue range, most effective in producing fluorescence in many substances

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3
Q

What’s chemiluminescence?

A

Production of light from a chemical reaction

two chemicals form an excited high energy intermediate which breaks down releasing some of it’s energy

Example is luminal - only used as last resort when think have missed everything

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4
Q

How to test for drugs?

A

Presumptive colour test for drugs

Quick and simple doesn’t require lots of training

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5
Q

Colour tests for drugs?

A

Marquis colour - amphetamine/methamphetamine

Cobalt thiocyanate - cocaine

Dillie - Koppanyl - Barbiturates

Eriich test - LSD

Duquenois-Levine Test - Cannabis

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6
Q

Colour test for bodily fluids?

A

Blood - TMB + hydrogen peroxide = green
Also Phenolpthalein = pink

Semen - SAP and Brentamine fast blue = purple

Saliva - starch iodine test - loss of blue colour

Sweat - Ninhydrin = pink

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7
Q

Colour test for gunshot residue?

A

Modified Greiss test - nitrite compounds = orange

Dithiooxamide test - metal elements, grey-green = copper, Blue pink = nickel

Sodium rhodizonate test - test for lead, = violet

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8
Q

Why reconstruct a crime scene?

A

It’s lost or destroyed

Depicting events

Explore hypotheses

Present findings

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9
Q

Precautions to take when looking at a reconstruction?

A

Because it’s on a computer doesn’t mean its right

Colour

Language

Assumptions

Don’t make it up

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10
Q

It is not `always what you see?

A

It’s what you don’t see

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11
Q

Good method in scaling a reconstruction scene?

A

Google furniture dimensions

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12
Q

Most important point about presenting to a jury?

A

Make it very easy to understand

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13
Q

Process of working out a crime scene?

A

Gather information and intelligence

Asses threat and risk and develop a working strategy

Consider powers and policy

Identify options and contingencies

Take action and review what happened

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14
Q

What happens to the DNA if a body is in the water for too long?

A

Degrades

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15
Q

Good thing to look out when looking at a body?

A

If they have had surgery, DNA, taking finger prints, teeth

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16
Q

What hinders investigations?

A

Investigator pareiodolia

Cognitive bias

Witness imperfect memory

Criminals unwillingness to be caught

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17
Q

Challenges of analytical techniques at a crime scene?

A

Very small samples = highly sensitive analytical techniques

Evidence is not usually a pure substance (contaminants)

Destructive techniques

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18
Q

Whats qualitative analysis?

A

Identifying and characterising matter

What is its chemical composition?
Where has it come from? (How did it get there?)

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19
Q

What’s quantitive analysis?

A

Quantifying the amount of a compound or element present
in a sample

What is the concentration of the chemical?
Is the concentration significant?

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20
Q

What’s preliminary analysis?

A
  • Simple, rapid, inform subsequent tests

Luminol, chemical analysis for biological fluids, gunshot residue, drugs

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21
Q

Types of microscopic analysis?

A

Optical (diatoms in aspirated water, pollen transfer when concealing a body) and electron (looking at surfaces)

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22
Q

What is separation of molecular spectroscopy?

A

Assesses electromagnetic properties of molecules and atoms undergoing transitions between energy levels.

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23
Q

Types of chemical analysis?

A

Molecular Spectroscopy

Elemental analysis

Mass Spectrometry

Chromatography

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24
Q

features of gun shot residue?

A

When a GSR population is found (at least one three-component particle is identified), a gunshot residue expert can say that it landed there in one of three ways:

The subject/object was in close proximity to a discharged firearm.
The subject/object came into contact with an object that already had GSR on it.

Size of particles depends on firing distance

BUT THIS CANNOT DETERMINE WHO MIGHT HAVE BEEN THE SHOOTER

Looked at with SEM-EDX Scanning electron microscopy used with energy dispersive x-ray (EDX) analysis

Pin impression can help link bullet to a gun

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25
Q

2 Types of useful chromatography?

A

Liquid and gas

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26
Q

Is mass spectrometry a destructive technique?

A

yes

Breaking down larger compound into characteristic fragments

27
Q

Isotope ratio mass spectrometry can be used for?

A

Identifying fish/meat intake from hair and finger nails

So can identify geographic location

28
Q

Good non destructive techniques?

A

UV-vis spectroscopy (paint, dyes on fibres, drugs analysis)

Infrared spectroscopy (looking at electric dipole moment) so looking at which bonds vibrate

29
Q

What sort of relationship is abosrbanec and concentration?

A

Linear

30
Q

What’s used for analysis of individual elements?

A

Atomic spectroscopy

31
Q

The Birmingham six case?

A

Griess test detected nitrite ions and nitro groups

Positive identification on the hands of IRA members

Was found that nitrites could be found in lots of other stuff so they were released

32
Q

The Jill Dando murder

A

Killed by close range shot in the side of her head

Found particles of gun shot residue on her head and coat

Similar particles found inside right hand pocket of Barry George seen in the location of the murderer

Then looked at elemental analysis

2008 was found that the evidence was not reliable

33
Q

Holly Wells and Jessica chapman case study?

A

girls went missing

Ian Huntley was caretaker at the school

Attempt to burn the bodies and clothes

Analysed fibres

Used comparison microscope and polarising microscopy - distinguish between made made and natural fibres

Showed there had been transferred of fibres between them enough for physical contact

Looked at the soil and pollen from the crime scene

34
Q

Glenn Turner and Randy Thompson?

A

She killed her husband and boyfriend

Died from flu then heart failure

It was antifreeze - ethylene glycol - not got rid of by the kidney - found in blood

35
Q

Stephen Lawrence?

A

Killed waiting for the bus

Blood stain found in suspects jacket

36
Q

Nathan Aleen 1979?

A

Stick of dynamite blew him up in his truck

Atomic absorption spectroscopy

grins test for nitrites

Plastic fragments used to make it allows you to find the manufacture

37
Q

Test for cocoaine?

A

Scotts test , Cobalt Thiocyanate

38
Q

What’s an SIO?

A

Leader of the team

Principal decision maker in cases of murder, rape, abduction or other serious crime.

Sufficient rank, normally detective inspector, detective superintendent, appropriately trained and experienced.

Responsible for Policy File

39
Q

What does a crime scene co ordinator do?

A

Directs the forensic investigation in
Complex major crimes
Major Crimes where there are multiple scenes
There maybe several Crime Scene Managers operating at the various scenes

40
Q

What does a crime scene manager do?

A

Directs all aspects of the forensic investigation at the scene of major crimes

41
Q

What does a Crime Scenes Investigator or SOCO do?

A

Carry out the tasks identified by the CSM at the scene of major crimes
Deals with all the forensic issues, examinations and recoveries at the scenes of volume or less serious crime

42
Q

Three tier examination strategy

A

Photography
Forensic
Fingerprinting

43
Q

Wound ballisitcs?

A

A missile has a kinetic energy of 1/2 mv^2

M = mass

v = speed

Missilesproduce a permanent cavity that equals the width of the object during its passage

Shock waves (need to finish this from slide)

tempory cavity?

44
Q

Types of ballistics?

A

Internal Ballistics
What happens within the first 2 ms of the shot being fired

External Ballistics
Flight of the bullet or shot after leaving the barrel

Terminal Ballistics
Inside the target or body
Dr Alisdair Dow

45
Q

Primer composition?

A 
Lead Styphnate
Barium Nitrate
Antimony Trisulphide
Calcium Silicide
Zirconium
Tetrazine

Primer can be shaped and located in different positions at the base of the round

46
Q

Describe rifling in the barrel?

A

Rifling in the barrel
Imparts left or right handed spin to the bullet
Up to 300 000 rpm for military assault rifles
Smooth Barrel
Shotgun
Choke

47
Q

Gun shot residue analysis?

A

Scanning Electron Microscopy
Energy Dispersive X-ray Analysis (EDAX)
Atomic Absorption
Inductively Coupled Plasma Spectroscopy
High Performance Liquid Chromatography (HPLC)
Gas Chromatography Mass Spectrometry (GCMS)

48
Q

Gun shot residue visualisation?

A 
Crime Scene Reagents
React with the Nitrates and Nitrites in the GSR – colour change
Diphenylamine (DPA)
Cotton Swab, DPA and Sulphuric acid
Dark Blue
Griess Test
Photographic paper and glacial acetic acid
Orange
49
Q

What do you need if you find DNA at the scene?

A

Known suspects for comparison or the database

50
Q

What are FTA cards?

A

Contain chemicals that lyse cells, denature proteins and protect nucleic acids from nucleases, oxidative, and UV damage (samples are stable for several years)

Used for offender DNA databases

Blood
Buccal swabs
Saliva

51
Q

Features of human chromosome set?

A

23 pairs (46 total) (maternal/paternal) described as homologous as they have the same size and contain the same genetic structure.

Different size and shape, largest denoted 1 etc.

Contain different genes

When chromosomes are stained with fluorescent dyes they develop distinctive patterns of bright and dark bands

52
Q

What are Short Tandem repeats?

A

Also called ‘microsatellites’
Forensics uses those that are 2 to 6 bases in length
Less susceptible to degradation so may be recovered after decomposition
Number of repeats is highly variable among individuals (5-20% will share the STR)
100s of different STRs in the human genome

53
Q

Describe STRs?

A 
Locus = genetic location
Allele = versions of the gene at the same location on the chromosome

Each individual will have two copies of each STR therefore increases discrimination

54
Q

What’s multiplexing?

A

Primers for many different loci (with STR regions) can all be used in the same reaction mix, will amplify both allele 1 and 2.

Primers are fluorescently labelled to aid detection.

Multiple products will be generated to obtain lots of information with only one DNA template

55
Q

What does capillary electrophoresis provide?

A

Each STR product will have a specific label

Different size STR products will be separated from each other by capillary electrophoresis

DNA-17 STR profiling –The National DNA Database (NDNAD) of England and Wales

Established on April 10th 1995 representing 9.6% of the UK population

56
Q

DNA profile for STR locus and no. repeats?

A

2 numbers if one from your mother, one from your father

One number if they are the same length

1/2 share parent and sibling

half sibling 1/4

cousins 1/8

57
Q

How to identify between twins?

A

Single nucleotide differences can occur every 1:10,00 bp throughout the genome after the blastocyst has split in two.

Hard to detect without full genome sequencing i.e. expensive.

58
Q

What to do if there is no DNA match?

A

Predict hair colour, eye colour, skin colour and ancestry

Reduce pool of candidates

59
Q

What’s irisPlex?

A

A multiplex genotyping assay and a prediction model based on genotype and phenotype data.

Can predict blue and brown eye colour

60
Q

What is HIresPlex?

A

22 SNP’s for hair colour prediction

Four overlap with eye colour

61
Q

What is skin colour determined by?

A

Skin colour is determined by concentration of epidermal melanin and therefore number of melanocytes/melanosomes

Reflectance can measure the skin pigmentation

Reflectance M-index (melanin index) is normally distributed amongst the population

62
Q

How to combine the phenotype measures?

A

Database enables input of alleles and calculated a predicted phenotype.

Certain SNPs are an absolute requirement due to their key role in determining

63
Q

Major effectors of facial shape?

A

Sex: affected the masculinity/femininity of many facial segments

BMI: affected large regions with underlying adipose tissues

Age: affected facial structure due to degrading of skin elasticity.

Human Biosciences (69 decks)

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