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Year 3 > Forensic biscience > Flashcards

Forensic biscience Flashcards

(86 cards)

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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
What aids maggots in feeding?
The release enzymes to further breakdown matter
26
What factors affect development times of larvae?
Temperature and population density
27
How can you tell if a maggot is a fully developed 3rd instar?
Clear gut
28
Why is it useful to know the geographical distribution of a species of blowfly?
To determine whether a body is likely to have been moved.
29
Why is it useful to know seasonal activity of a species of blowfly?
To estimate PMI
30
Calliphora vicina
``` 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 ```
31
Lucilia sericata
``` Diurnal 2000-3000 eggs in 9-10 batches Arrive within hours Adults prefer bright sunshine Eggs laid in shade, e.g. nose ```
32
Phormia terraenovae
``` Cooler parts of Europe Diurnal Early spring (before Lucilia) Develop faster than other blowfly Pupate on corpse ```
33
Phorid flies
Can access areas that blowflies are too big for (e.g. coffin fly)
34
Phiophild flies
Usually present when body is starting to dry out
35
Stratiomyid flies
Often found on buried bodies
36
Dermestid beetles
Colonise once body starts to dry out
37
Myiasis
Wounds infected with larvae
38
Ectoparasite
Parasites of body surface
39
If lice are observed on a dead body, what may this indicate?
The person has not been dead long as lice and fleas usually leave soon after death as temperature decreases
40
How long after a blood meal is it possible to extract DNA from fleas or lice to link people together?
72 hours
41
How may invertebrates indicate neglect of an individual?
Myiasis of wounds
42
Why should care be taken when collecting invertebrates from a body?
They may have ingested transmissible diseases
43
What data should be collected from the scene for estimation of oviposition date?
``` Air, soil, body temp Vegetation Geographical location Date & time found Position of body Soil conditions Weather conditions Presence of other decaying matter ```
44
What are the benefits of ADD calculations?
They are relatively simple and are widely accepted?
45
What are the limitations of ADD calculations?
They assume that development is constant
46
What factors can result in an underestimate of oviposition date?
``` fly access insecticide diapause predators drugs/toxins ```
47
What factors can result in an overestimate of oviposition date?
Myiasis prior to death maggot feeding mass drugs/toxins
48
How can invertebrates be used to determine whether a body has been moved?
Many have restricted distribution or occupy certain habitats
49
Apart from DNA, what else can be analysed from the gut contents of maggots?
Drugs
50
Why are seeds useful for indicating the time of year someone died?
They are seasonal
51
How are plants identified?
Using morphology or DNA if they look too similar
52
What is the exine?
The outer layer of a pollen grain that is resistant to degradation.
53
What factors may affect how far wind pollinated grains will travel?
``` Height of release Release mechanism Strength of wind Weight/shape of grain obstructions ```
54
What is another word for wind pollinated grains?
Anemophilous
55
How are diatoms normally identified?
Based on morphology
56
What are frustules?
Cell walls of algae made up of silica
57
What are diatoms usually considered in relation to?
Drowning
58
Which enzyme converts RNA HIV to DNA?
Reverse transcriptase
59
Why does HIV have a high mutation rate?
Unlike DNA polymerase, viral reverse transcriptase does not proof read
60
How may JCV and BKV viruses help a forensic case?
They have local variations and may link a person to a location.
61
'which gender has the highest suicide rate?
Males
62
Wound
Broken skin
63
Counter-pressure bruising
Someone held against hard surface
64
Suspension peak
Common in suicides - area of neck with no ligature furrow
65
Laceration
Skin stretches and tears
66
Incised wound
Slash or cut
67
Smooth bore
Firearms that lack rifling
68
Rifling
Spiral pattern of grooves
69
Calibre
Internal diameter of barrel
70
Contact wound
Gun pressed against flesh and sears the skin when fired
71
Precession
Bullet rotates around its centre of mass
72
What does a gun cartridge contain?
Primer, propellant, bullet/shot
73
What is powder tattooing?
Burns caused by hot propellant
74
Why do arthropods shed their exoskeleton?
To allow for growth
75
What are precocious eggs?
Single fertilized eggs that will be at a further stage of development than others laid at the same time.
76
What distinguishes Sarcophagid flies?
They give birth to live young
77
How can larvae be aged?
Morphology of posterior spiracles, length, extent of tanning of pupae, x-ray of pupae
78
DNA from pupae case study
- 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
Calculation for time since oviposition
Time (days) x (temp - base temp)
80
What is the base temperature?
The minimum temperature at which species will continue developing.
81
Neglected cerebral Palsy patients study
- 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
Pollen calendar study
- Montali et al, 2006 - Pollen is a seasonal marker - Face is most useful as traps pollen in season of death
83
How does subcutaneous fat affect bruising?
Where there is more of it (e.g. buttocks), bruising occurs more easily.
84
Where are lacerations most common?
Areas where the skin is thin, e.g. shins
85
Why does the skin become pale after death?
Blood circulation ceases which deprives cells and tissues of oxygen so they die.
86
Why is a measurement potassium ion concentration of the vitreous humour of the eye taken?
to estimate PMI, but chemical changes are not commonly used or widely accepted for PMI estimation.

Year 3 (2 decks)

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