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Year 3 > Forensic biscience > Flashcards

Forensic biscience Flashcards

1
Q

What are the 5 stages of decay?

A
  1. Fresh
  2. Bloat
  3. Active decay
  4. Advanced decay
  5. Putrid dry remains
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2
Q

How long does a body usually take to reach the bloat stage in temperate climates?

A

4-6 days

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3
Q

What factors may increase the rate of cooling of a body?

A
  1. Small body size
  2. Low fat content
    .3. Lots of blood loss
  3. Wet/absent clothes
  4. Low ambient temp
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4
Q

What factors may decrease the rate of cooling of a body?

A
  1. Large body size
  2. High fat content
  3. Foetal position
  4. Clothing
  5. High humidity
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5
Q

Where is potassium ion concentration measured from?

A

Vitreous humor of the eye

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6
Q

How to distinguish skin splitting post-mortem from a peri-mortem injury?

A

Less blood loss post-mortem

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7
Q

The longer a person has been dead….

A

The greater the error of estimation of time since death

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8
Q

What is algor mortis?

A

Body cooling after death. Temp should be taken from rectum to measure core, however, this may disturb evidence.

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9
Q

How long does livor mortis take to set in?

A

20-120 minutes. After 10-12 hours, the discolouration will become fixed and any movement will be obvious.

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10
Q

What is pressure pallor?

A

Areas of the body that do not change colour. E.g. back from lying on floor, bra straps, ropes.

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11
Q

What may influence rate of livor mortis?

A

circulatory diseases

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12
Q

How long until body is rigid?

A

12 hours

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13
Q

What causes rigor mortis?

A

Calcium ions move down their concentration gradient and troponin and tropomyosin move aside causing cross-bridges which don’t detach as ATP is not formed.

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14
Q

What is cadaveric rigidity?

A

Instantaneous rigor

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15
Q

How to distinguish putrefactive rigor from rigor mortis?

A

Putrefactive rigor accompanies marbling and smell

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16
Q

What conditions are usually needed for adipocere formation?

A

anaerobic

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17
Q

Detritivores

A

Feed on decaying tissues

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18
Q

Coprophiles

A

Feed on faeces

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19
Q

Predators

A

Prey on detritivores

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20
Q

Parasitoids

A

Use another animal as a host

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21
Q

How many eggs may a gravid female blowfly lay?

A

Up to 180

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22
Q

Where do blowflies typically lay eggs?

A

Nose, ears, mouth, eye, wound etc.

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23
Q

What attracts blowflies to a corpse?

A

The smell of blood

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24
Q

When are blowfly active?

A

During the day when temperature is higher

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25
Q

What aids maggots in feeding?

A

The release enzymes to further breakdown matter

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26
Q

What factors affect development times of larvae?

A

Temperature and population density

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27
Q

How can you tell if a maggot is a fully developed 3rd instar?

A

Clear gut

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28
Q

Why is it useful to know the geographical distribution of a species of blowfly?

A

To determine whether a body is likely to have been moved.

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29
Q

Why is it useful to know seasonal activity of a species of blowfly?

A

To estimate PMI

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30
Q

Calliphora vicina

A 
Worldwide.
Large.
Unlikely to lay eggs below 12 degrees
Unlikely to hatch below 4 degrees
Lay up to 300 eggs
Disperse 6-7 metres to pupate
Bluebottle
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31
Q

Lucilia sericata

A 
Diurnal
2000-3000 eggs in 9-10 batches
Arrive within hours
Adults prefer bright sunshine
Eggs laid in shade, e.g. nose
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32
Q

Phormia terraenovae

A 
Cooler parts of Europe
Diurnal
Early spring (before Lucilia)
Develop faster than other blowfly
Pupate on corpse
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33
Q

Phorid flies

A

Can access areas that blowflies are too big for (e.g. coffin fly)

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34
Q

Phiophild flies

A

Usually present when body is starting to dry out

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35
Q

Stratiomyid flies

A

Often found on buried bodies

36
Q

Dermestid beetles

A

Colonise once body starts to dry out

37
Q

Myiasis

A

Wounds infected with larvae

38
Q

Ectoparasite

A

Parasites of body surface

39
Q

If lice are observed on a dead body, what may this indicate?

A

The person has not been dead long as lice and fleas usually leave soon after death as temperature decreases

40
Q

How long after a blood meal is it possible to extract DNA from fleas or lice to link people together?

A

72 hours

41
Q

How may invertebrates indicate neglect of an individual?

A

Myiasis of wounds

42
Q

Why should care be taken when collecting invertebrates from a body?

A

They may have ingested transmissible diseases

43
Q

What data should be collected from the scene for estimation of oviposition date?

A 
Air, soil, body temp
Vegetation
Geographical location
Date & time found
Position of body
Soil conditions
Weather conditions
Presence of other decaying matter
44
Q

What are the benefits of ADD calculations?

A

They are relatively simple and are widely accepted?

45
Q

What are the limitations of ADD calculations?

A

They assume that development is constant

46
Q

What factors can result in an underestimate of oviposition date?

A 
fly access
insecticide
diapause
predators
drugs/toxins
47
Q

What factors can result in an overestimate of oviposition date?

A

Myiasis prior to death
maggot feeding mass
drugs/toxins

48
Q

How can invertebrates be used to determine whether a body has been moved?

A

Many have restricted distribution or occupy certain habitats

49
Q

Apart from DNA, what else can be analysed from the gut contents of maggots?

A

Drugs

50
Q

Why are seeds useful for indicating the time of year someone died?

A

They are seasonal

51
Q

How are plants identified?

A

Using morphology or DNA if they look too similar

52
Q

What is the exine?

A

The outer layer of a pollen grain that is resistant to degradation.

53
Q

What factors may affect how far wind pollinated grains will travel?

A 
Height of release
Release mechanism
Strength of wind
Weight/shape of grain
obstructions
54
Q

What is another word for wind pollinated grains?

A

Anemophilous

55
Q

How are diatoms normally identified?

A

Based on morphology

56
Q

What are frustules?

A

Cell walls of algae made up of silica

57
Q

What are diatoms usually considered in relation to?

A

Drowning

58
Q

Which enzyme converts RNA HIV to DNA?

A

Reverse transcriptase

59
Q

Why does HIV have a high mutation rate?

A

Unlike DNA polymerase, viral reverse transcriptase does not proof read

60
Q

How may JCV and BKV viruses help a forensic case?

A

They have local variations and may link a person to a location.

61
Q

‘which gender has the highest suicide rate?

A

Males

62
Q

Wound

A

Broken skin

63
Q

Counter-pressure bruising

A

Someone held against hard surface

64
Q

Suspension peak

A

Common in suicides - area of neck with no ligature furrow

65
Q

Laceration

A

Skin stretches and tears

66
Q

Incised wound

A

Slash or cut

67
Q

Smooth bore

A

Firearms that lack rifling

68
Q

Rifling

A

Spiral pattern of grooves

69
Q

Calibre

A

Internal diameter of barrel

70
Q

Contact wound

A

Gun pressed against flesh and sears the skin when fired

71
Q

Precession

A

Bullet rotates around its centre of mass

72
Q

What does a gun cartridge contain?

A

Primer, propellant, bullet/shot

73
Q

What is powder tattooing?

A

Burns caused by hot propellant

74
Q

Why do arthropods shed their exoskeleton?

A

To allow for growth

75
Q

What are precocious eggs?

A

Single fertilized eggs that will be at a further stage of development than others laid at the same time.

76
Q

What distinguishes Sarcophagid flies?

A

They give birth to live young

77
Q

How can larvae be aged?

A

Morphology of posterior spiracles, length, extent of tanning of pupae, x-ray of pupae

78
Q

DNA from pupae case study

A
  • McDermid, 2014
  • Large number of pupal cases found in loft
  • sent for toxicology and found heroin metabolites
  • DNA of pupae (old skin) contained human DNA from a missing addict.
79
Q

Calculation for time since oviposition

A

Time (days) x (temp - base temp)

80
Q

What is the base temperature?

A

The minimum temperature at which species will continue developing.

81
Q

Neglected cerebral Palsy patients study

A
  • Ramli & Rahman, 2002
  • 15 YO and 19 YO had maggots in palates
  • Poor oral hygiene and persistent mouth opening
  • 15 YO also in ear
  • Parents did not bring back for review appointment
82
Q

Pollen calendar study

A
  • Montali et al, 2006
  • Pollen is a seasonal marker
  • Face is most useful as traps pollen in season of death
83
Q

How does subcutaneous fat affect bruising?

A

Where there is more of it (e.g. buttocks), bruising occurs more easily.

84
Q

Where are lacerations most common?

A

Areas where the skin is thin, e.g. shins

85
Q

Why does the skin become pale after death?

A

Blood circulation ceases which deprives cells and tissues of oxygen so they die.

86
Q

Why is a measurement potassium ion concentration of the vitreous humour of the eye taken?

A

to estimate PMI, but chemical changes are not commonly used or widely accepted for PMI estimation.

Year 3 (2 decks)

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