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Forensic medicine > CSI Dundee > Flashcards

CSI Dundee Flashcards

1
Q

Locard’s exchange principle

A

“every contact leaves a trace”

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2
Q

Describe ‘jigsaw’ evidence

A

Physical match between part of substance on victim and other part on attacker.

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3
Q

what are the main examples of trace evidence found on clothing?

A

hairs, fibres, glass, paint, GS residues, vegetation, pollens

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4
Q

how is paint analysed as trace evidence?

A

flakes of paint on clothing can be microscopically examined to determine the layer structure and thickness for the paint and matched with another sample e.g. from a suspected car in a hit and run

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5
Q

vomit can stain clothing and be analysed. a pink-tinged vomit might indicate the victim ingested what?

A

amitriptyline can tinge vomit a pink colour and can be used in overdose

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6
Q

what can the pattern of a blood stain tell you?

A

if the victim was standing or lying down when injured
e.g. a person standing up that stabs themselves would have blood flowing down following gravity and might have moved clothing out the way - if blood stain is horizontal then they were lying down
if clothing is in the way of the injury and also stained, this might suggest an attack over suicide.

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7
Q

Give examples of low velocity blood patterns.

A

dripping, cast-off from weapon, splashing or arterial spurting

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8
Q

Give an example of a medium-velocity blood pattern.

A

baseball bat injury

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9
Q

Give examples of high velocity blood patterns.

A

gunshots or machinery related injuries

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10
Q

The higher the velocity of the injury, the larger the droplets of blood - true or false

A

FALSE
the higher the velocity, the smaller the droplets
e.g. HV gunshot -> fine mist

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11
Q

The smaller the droplets, the further they can travel in air - true or false

A

FALSE
smaller droplets travel shorter distance in air
e.g. fine mist from gunshot would only hit those in close proximity to victim

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12
Q

What test can be done at a crime scene to confirm presence of blood in a stain?

A

Leuco Malachite Green

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13
Q

What are the pros of Leuco Malachite Green?

A

it is a minimally destructive chemical test

It can be used at the scene

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14
Q

When assessing the point of convergence, shorter and fatter blood splatters hit the surface at a smaller angle - true or false?

A

true

shorter + fatter blood splatters hit surface at smaller angle

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15
Q

How do you assess convergence in 2D?

A

draw lines through splatter to find direction of infliction

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16
Q

Describe a typical arterial spurt pattern and in which situation it would be seen.

A 
up and down cycle = arterial spurt
common in (suicidal) neck incisions
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17
Q

Blood transfer/smearing noticed on wall in a brush stroke pattern - what does this suggest?

A

a bleeding head wound or blood stained hair wiped along the wall.
the height of the smear on the wall tells you if person was standing or crawling

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18
Q

Mud or soil can be used as evidence, where will you look for it?

A

sources: clothing, footwear and tyres especially

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19
Q

What is noted about evidential mud/soil?

A

colour when dry
particle size & density
mineral composition
biological composition (plants, pollens, microbiology)

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20
Q

a mud/grass stain on the seat of jeans suggests what?

A

wearer was dragged by legs

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21
Q

plant pollens are fragile particles - true or false

A

FALSE

plant pollens are highly resistant particles

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22
Q

what can paint pollens be used to confirm?

A

they can confirm a suspect was in a particular area and also tell you at what time of year and sometimes what time of day - due to seasonal and diurnal variation

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23
Q

Where can you take pollen samples from?

A 
soil
cars (tyres, wheel arches, upholstery)
hair
clothes, shoes
under fingernails
nasal cavities
gut
firearms 
other substances (drug packages, explosives)
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24
Q

what is probably the most common type of trace evidence?

A

fibres

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25
Q

a forensic scientist is usually able to individualise fibres provided as evidence - true or false

A

FALSE

due to mass production, it is not usually possible to individualise fibres

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26
Q

Examples of animal fibres.

A

animal fibres = proteins
silk = fibroin
wool and hair = keratin

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27
Q

Examples of vegetable fibres.

A

veg fibres = cellulose - seed, stem and leaf fibres

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28
Q

Example of a mineral fibre.

A

asbestos

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29
Q

More common fibres have less evidential value - true or false

A

true

more common fibres like denim have less evidential value

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30
Q

Describe the possible mechanisms of transfer of fibres.

A
  1. Loose fibres may shed.
  2. Embedded fibres may be pulled out or shed.
  3. Fibres can break under stress > shed
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31
Q

what techniques can be used to examine fibres?

A

microscopy - comparison, polarised light, light, UV light
Infra-red spectroscopy
chromatography

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32
Q

Fibres examined under light and comparison microscopy look identical but once under polarised light, some differences are noted - do they still count as a match?

A

no, once a difference is recognised they are no longer considered the same

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33
Q

DNA can be detected in saliva. What are some potential sources of saliva?

A

apart from obvious spit, bite marks, stamps/envelopes, cigarettes, drinking glass

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34
Q

What samples associated with a person’s scalp might offer DNA samples?

A

dandruff and hair follicles

hats

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35
Q

Semen is the main source of DNA related to males in sexual incidents, but how might you identify a female victim if you have the male suspect?

A

vaginal/endometrial cells from victim can rub off onto penis and persist for around 24hrs
these cells might be found on the suspect’s underwear

a used condom will have male DNA on inside but vaginal/anal cells on outside (gives you victim and attacker)

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36
Q

normal pH of semen

A

pH 7.2-8.0

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37
Q

main components of semen

A 
spermatozoa
acid phosphatase (AP)
Prostatic specific antigen P30 (PSA)
choline
spermine
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38
Q

how long can motile sperm last in vaginal canal?

A

usually only live 4-6hrs in acidic vaginal canal

not normally found >16hrs after intercourse

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39
Q

how long do non-motile sperm last in vaginal canal?

A

in upper vagina, up to 3d after sex, sometimes >6d in cervix

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40
Q

Apart from drainage, how else might spermatozoa be lost as evidence following sexual intercourse?

A

(drainage)
dilution: vaginal secretions, saliva
degradation: seminal enzymes, loss of tails
defaecation
washing/showering after sex

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41
Q

how long can sperm last in mouth - what does this mean for swabs?

A

<6-12hrs in mouth

swab <2d

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42
Q

how long can sperm last in upper vagina?

A

<6-12hrs if motile

<3-6d if non-motile

43
Q

how long can acid phosphatase last in upper vagina?

A

AP <48hrs

44
Q

how long can sperm last in the endocervical canal?

A

7-10 days

45
Q

how long after intercourse can you swab vagina for spermatozoa?

A

upper vagina swab <7d

46
Q

how long can sperm last in anus and rectum - what does this mean for swabs?

A

anus: <2d
rectum: <3d
swab rectum <3d

47
Q

What lab samples do you take from a female victim of sexual assault?

A 
clothing
head hair
swabs of mouth/saliva
fingernail scrapping, clippings ± swabs
skin swabs
pubic hair 
vaginal swabs
ano-rectal swabs 
blood
48
Q

what swabs do you take of bite?

A

moist and dry swab

49
Q

What is the swabbing technique required for vaginal swabs (timescale + no.)?

A 
take them within 7 days 
vulva: double swab technique
lower 1/3 (3-5cm): 2x dry
upper 2/3 (speculum): 2x dry 
endocervical canal: 2x dry
50
Q

What is the swabbing technique for ano-rectal swabs?

A

take within 3 days
perianal skin-3cm radius from anus: double swab technique
anal canal (rotate at 2-3cm): 2x dry
rectum (proctoscope, >4cm): 2x dry

51
Q

When and how do you collect a mouth swab?

A

collect if oral penetration occurred within 2 days
2x dry swabs rubbed over + under tongue, over all sides of teeth, gums and inside cheeks.
mouth rinse with sterile water into polypot (police kit)

52
Q

when do you collect a vaginal swab?

A

digital penetration <12hrs
vaginal intercourse <7d
anal intercourse <3d

53
Q

When do you collect anal swabs?

A

digital penetration <12hrs

anal intercourse <3d

54
Q

what is the swabbing technique for penises?

A

double swab technique for shaft, foreskin/coronal sulcus and glans

55
Q

what laboratory technique is diagnostic for spermatozoa

A

microscopy

56
Q

Acid phosphatase if detected, confirms semen was present - true or false

A

FALSE
AP is not specific for semen -> false positives

AP is found in low concentrations in vaginal secretions and other bodily fluids

57
Q

PSA if detected, confirms semen was present - true or false

A

PSA is secreted into seminal fluid and is an accepted marker for semen in criminal cases

58
Q

If a male suspect is believed to have had a vasectomy, how can you test trace evidence for sexual intercourse?

A

PSA is a good marker for semen in persons lacking DNA in sperm e.g. azoospermia or in those who have had a vasectomy

59
Q

how long is AP detectable after ejaculation and what colour test is used?

A

detectable up to 48hrs after

colour test: purple in <30s = positive

60
Q

a flame-shaped hair root which is attached to the follicle is seen in which phase of hair growth?

A

anagen phase

61
Q

an elongated root shape and slow growth is seen in which phase of hair growth?

A

catagen phase lasts 1-3 weeks and is slow growth with elongated root shape

62
Q

a club-shaped root is seen in which hair growth phase?

A

telogen phase lasts 2-6 months and has a club-shaped root

63
Q

Hair cuticles have a resemblance to which structure and what do they indicate?

A

overlapping scales of keratin resembling roof tiles

the cuticle pattern indicates species

64
Q

which part of hair contains pigment granules

A

cortex of hair contains pigment granules

the colour, shape and distribution of these granules is important

65
Q

which part of hair structure is arranged in parallel spindle cells in regular parallel way?

A

cortex

66
Q

The medullary canal of a hair strand is always continuous - true or false

A

false

can be continuous, interrupted, fragmented or absent

67
Q

what can the medulla of hair tell you about the person?

A

if medullary canal is absent or interrupted it can indicate race.
it will be a continuous canal in monogloid persons

68
Q

what can the morphology of the scales, cortex and medulla of hair tell you?

A

the body area, racial origin, sex (bleching, dyeing) and age of a person

69
Q

if hair is forcibly removed what will also be seen microscopically?

A

sheath cells seen if force used

70
Q

comparison of hair strands can individualise persons - true or false

A

false comparison of strands (without DNA) cannot individualise

71
Q

what kind of samples can be taken during arrest?

A

non-intimate samples - fingerprints, palm prints, other impressions, photographs

72
Q

What kind of samples can be taken during arrest if inspector gives permission?

A

body hair (not pubic)
finger/toe-nail clippings or other nail material
blood or other body tissues or fluid gained by swabbing or rubbing
saliva that can be swabbed from the inside of the mouth

73
Q

blood samples are a routine sample taken on arrest - true or false

A

false

blood samples can be taken with a warrant

74
Q

upon detention or arrest, police have the power to carry out DNA test - true or false

A

true

= cells scrapped/swabbed from inner cheek lining

75
Q

What does the National DNA database hold?

A

DNA profiles from those arrested or charged with, or convicted of a recordable offence
also DNA profiles obtained from crime scenes

76
Q

What are the 6 benefits of the National DNA database?

A
  1. Early identification of linked cases (serial crimes)
  2. Early arrest of offenders
  3. Valuable intelligence
  4. Early exoneration of innocent suspected
  5. Easier identification of bodies
  6. Deterrence
77
Q

Police takes prints and impressions of suspect - when will these be destroyed?

A

destroyed if don’t get convicted of crime
if convicted, prints, impressions & DNA records can be held for up to 2 years (or 3 if a particular violent or sexual offence) if the accused accepts an alternative to prosecution e.g. a fine or work order

78
Q

How long can DNA and prints from a violent ± sexual offence be kept for by the police?

A

for up to 3 years even if accused is acquitted by court or case is dropped.

police can also apply for an extension of up to 2 years at a time

79
Q

urine is classed as an intimate sample - true or false

A

true

so is blood and dental impressions

80
Q

consent is always sought for an intimate sample - true or false

A

TRUE
However, an intimate sample can be taken from a person in police detention on authority of the Inspector if there are reasonable grounds for suspecting the involvement of the person in a recordable offence and that this sample will confirm or disprove this

81
Q

a doctor can take an intimate sample without consent - true or false

A

TRUE … in theory, however unlikely in real life

Inspector can order this but not many Drs will risk their license

82
Q

what swabbing technique is performed for fingernail scrapping?

A

2 swab technique (1 wet 1 dry)

83
Q

what is the double swab technique?

A
  1. moistened swab rolled over skin - rehydrates and loosens foreign cells
  2. dry swab rolled over same area - picks up foreign cells
84
Q

vaginal swabs are taken from endocervical canal > upper vagina > lower vagina > vulva - true or false

A

FALSE

swabs must be taken from outside in to avoid contamination of samples

85
Q

why is double swab technique used?

A

this technique results in higher recovery of cells/DNA and is used on skin (bit), vulva and penis

86
Q

When labelling specimens, what needs to be documented?

A 
name of subject
type of specimen
date & time collected
name of collector (FME or nurse)
name of witness (nurse)
name of police officer
87
Q

The supernatent acquired from extraction of material on vaginal swab is tested for what?

A

stained with H&E for sperm identification
supernatant tested for Acid phosphatase, amylase, ABO, choline
cellular fraction remaining is combined with expressed swab and used for DNA profiling

88
Q

what is the chain of custody?

A

the legal term that refers to the ability to guarantee the identity and integrity of the specimen from collection through to reporting of the test results.

process used to maintain and document the chronological Hx of the specimen

89
Q

what happens if the chain of custody is prolonged or messy?

A

the defence lawyers will say that the evidence is unreliable

90
Q

stress marks of glass fracture are aka. ?

A

Wallner lines - seen along edges

91
Q

what do stress marks on fractured glass show?

A

show direction from which pane was broken

92
Q

Radial cracks have ridges at ? angles to the ? face

A

radial cracks have ridges at right angles to the rear face (all r)

93
Q

Concentric cracks look like ?

A

spider’s web

94
Q

concentric cracks have ridges at ? angles to the ? face

A

concentric cracks have ridges at right angles to the front face

95
Q

Why does tempered glass tend to shatter?

A

it is less flexible due to heating and cooling process it has been through

96
Q

What modification has been added to car windscreen glass?

A

windscreens are now laminated (plastic sheet in middle of glass) to prevent ejection of passenger in RTA

97
Q

a bullet passes through glass, how can you tell the direction it was traveling in?

A

bigger proportion of glass shattered on side the bullet was travelling to
i.e. side of glass the bullet exited from has larger amount of broken glass

98
Q

a crowbar leaves a 3D mark in the softer windowpane - what is this type of mark called?

A

3D marks in soft material = impression

99
Q

a crowbar leaves a 2D scratch on the windowpane surface - what is this type of mark called?

A

2D linear scratching of surface = striation

100
Q

tool marks can tell you the type of tool and shape as well as any individual imperfections - true or false

A 
true 
class characteristics tell you general groupings such as tool type, size and shape
individual characteristics tell you any unique features of a weapon (transient or permanent)
101
Q

give an example of a transient individual characteristic?

A

e.g. a stone trapped in shoe grip will imprint but stone can fall out = transient

102
Q

footwear can make marks in mud, sand and snow - what kind of marks are these?

A

impressions in soft material (3D) = mud, sand, snow

103
Q

footwear can make marks in blood, dirt, or dust - what kind of marks are these?

A

prints on hard surface (2D) = blood, dirt, dust

104
Q

A person who was shot with gun pressed/very close to chest - what can the trace evidence tell you?

A

muzzle imprint - e.g. 12G shot gun + which barrel (right/left)
soot - elemental components

Forensic medicine (10 decks)

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