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Contemporary issues in biology 2Y > Forensics > Flashcards

Forensics Flashcards

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1
Q

What is Locard’s principle?

A

Every contact leaves a trace (important to avoid cross-contamination.

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2
Q

What is trace evidence?

A

very small pieces of material which have been left and provide a link to an individual

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3
Q

Explain methods of recovering trace evidence

A

taping/ vacuuming/ swabbing/ hand picking/ extracting…

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4
Q

What are some sources of DNA found in crime scene ?

A

Glass/ fibres/ seamen/ saliva / blood/

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5
Q

Define forensic science

A

application of scientific methods and techniques to maters under investigation

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6
Q

What are factors to consider about blood when used as trace evidence?

A

blood stains - examining shapes and location can indicate events which occurred

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7
Q

How can you test for the presence of seamen?

A

miscopy of a the seamen sample which acid phosphatase has been added to , if sample turns purple seamen is present

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8
Q

What test can be used to test for saliva ?

A

starch/ iodine test ->if saliva is present saliva amylase will turn the black colour blue.

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9
Q

Which tests can be used to test for blood samples.

A

Leuchomalachite green test (LMG becomes reduced and when hydrogen peroxide is added the substance becomes green therefore indicating the presence of blood /// Kastle Meyer test uses the same principle and turns red

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10
Q

What are the two main principles in forensic science?

A

Locards exchange (every contact leaves a trace) and Physical fit (The evidence must be strong enough to create a link between the individual and the crime.

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11
Q

What are some effects from alcohol? When do they occur?

A

50mg/100ml = slurred speech/ co-ordination loss/// 100-150mg= nausea/// 150-200mg = nausea and non co-operative/// 200-300 = comba…. 400=death

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12
Q

What enzymes are involved in alcohol metabolism?

A

alcohol dehydrogenase (ADH)

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13
Q

What factors determine variance in alcohol metabolism in individuals?

A

liver size / body mass/ food intake

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14
Q

How are alcohol concentrations in the body determined ?

A

contact time with GI/ quantity of alcohol consumes/ concentration/ food intake/

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15
Q

How is alcohol cleared from the body

A

Ethanol is broken down by alcohol dehydrogenase into acetaldehyde which is then broken down in carbon dioxide and water

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16
Q

How is alcohol concentration measured within the body?

A

electrochemical fuelled breathalyser // infrared optical sensor breathalyser // dual sensor breathalyser / gas chromatography

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17
Q

What is the equation used to calculate alcohol elimination?

A

Cmax - (t X elimination rate )
maximum alcohol concentration -( time X elimination rate)

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18
Q

What is the elimination rate for individuals with :
average metabolism?
fast metabolism ?
slow metabolism?

A

average = 18 // slow = 9// fast =27

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19
Q

What does dosis factin venenum belive about poisonous?

A

Everything has the potential to be poisonous, it is the amount of it which determins if it is poisonous or not

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20
Q

What is meant by temporary class of drugs?

A

categorises illegal drugs which are chemically different to those found in another class

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21
Q

What is a forensic toxicologist?

A

investigates the presence or absence of compounds in relation to the law

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22
Q

What cases would be toxicologist be involved in?

A

Road traffic acts offences / drink driving/ drug driving / drug-facilitated sexual assault / sudden or suspious deaths

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23
Q

Be aware of overarching theme of the misuse of drug act.

A
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24
Q

What are some analytical techniques used to identify drugs

A
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25
Q

What are some negative impacts of ecstacy?

A

effects temperature regulation // muscle cramping// blurred vision

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26
Q

What are the three main categories of drugs?

A

stimulates- stimulates brain / depressants- primary inhibits brain activity / hallucinogens- induces alterations in perception and mood

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27
Q

Give some examples of stimulates.

A

Amphetamines / cocaine

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28
Q

Give some examples of drugs in the category of depressants.

A

Alcohol/ Heroin / Benzodiazepines

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29
Q

Give examples of methods of analysing drugs

A

Presumptive tests / thin layer chromatography/ HPLC/ Mass spectrometry / Spectroscopy/ Immunaoassy

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30
Q

What is the aim of the majority of methods used to analyse drugs. (e.g. chromatography)

A

Separate components based on size and polarity

31
Q

What is meant by synaptic plasticity?

A

Synapses change dose needed to create a response.

32
Q

What are some negative effects of cocaine?

A

constricted blood vessels / nausea / raised blood vessels/ tremors / restlessness

33
Q

How do you calculate probability of having a particular STR patten at one locus?

A

frequency of one allele X frequency of another allele // ***if heterozygote must multiply the answer by 2

34
Q

What is an STR?

A

short tandem repeat - something which involves repeats between 1-6 base pairs

35
Q

Why do forensics examine the STR patterns of several locus?

A

to ensure results are more reliable / allows a profile to be created despite certain areas of DNA being degraded

36
Q

What is a partial profile and can it provide any useful information?

A

DNA analysis which does not cover all loci, can still create a comparison between samples and individuals but the results will not be as reliable (good for degraded DNA )

37
Q

What is familial screening?

A

Screening and profiling the DNA of an entire family. Allows heritable diseases to be identified

38
Q

Give some examples of uses for DNA profiling

A

identifying criminals / identifying illegal trade of wild animals i.e ivory / understand meat content of food

39
Q

What are some issues with DNA evidence?

A

human error / technical failure / contamination / PCR stutter (polymerase slips

40
Q

What are the 3 possible outcomes from DNA profiling?

A

exclusion = non-match/ inclusion = match// inconclusive

40
Q

How are blood groups determined?

A

by the antigen present (e.g. group A has antigen A present)

41
Q

What does it mean if an individual is a ‘secretor’?

A

HAVE THE FUT2 GENE //The individual secretes fluids (can be saliva/ blood/sweat…) secretors have a higher concentration of A and B antigens – more likely to be identified in crime scenes

42
Q

Give some examples of good biological sources of DNA which may be found in a crime scene?

A

WBC - large nucleus// Sperm cells / Hair shafts with roots

43
Q

Which sections of DNA are most useful for identification of individuals?

A

SNPs/ STRs are the main DNA variation individuals have

44
Q

In scenarios where twins are involved in crime what additional factors can be considered rather than sections of DNA?

A

epigenetic markers= modifications of DNA due to environmental factors, alike diet/ smoking…

45
Q

How do we get STRs?

A

During ‘slippage’ and miss realignment with the process of replication

46
Q

Where do we inherit mitochondrial DNA from?

A

mother, maternal DNA

47
Q

What are some methods of DNA profiling?

A

RFLP (restriction fragment length polymorphisms )= // PCR // mitochondrial DNA / Y-STR testing

48
Q

What is RFLP DNA profiling?

A

measuring and detecting different lengths of DNA after restriction-enzyme digestion.

49
Q

How can you calculate the probability of an individual having the named pattern of alleles?

A

frequency of allele 1 X frequency of allele 2
*if heterozygotic multiply this by 2

50
Q

What are some issues with DNA evidence?

A

Degraded DNA/ Human error/ technical failure/ contamination / PCR stutters

51
Q

What is the amylogenic locus, how does it help us determine the gender of an individual?

A

AMYLE X (X-chromosome) or AMYLE Y(y chromosome ) is present in every individual

52
Q

What is partial screening?

A

DNA screening which identifies the suspect to be of close relative of samples you have

53
Q

What are some additional uses of DNA profiling aside from criminal cases?

A

identification after natural disasters/ used in wildlife to find origins of animals, identify smuggling/ understand meat content / conservation

54
Q

How can insects be used as evidence for PMI?

A

understand if the body has been moved (urban to rural) // circumstances around death (aquatic animals = interaction with water)

55
Q

Why are insects good for forensic science?

A

Have regular and fast development (can identify how long an insect has been present for / life cycles are known) // they are small so can be analysed in labs easily // feeding - can indicate the presence of drugs // determine location of death

56
Q

What properties of plants make them valuable to forensic science?

A

identify locations (plant traces) // pollen is a very good trace source // poisonous plants can be seen as a weapon // environmental context via pollen or plant fragments

57
Q

What properties of plants make them valuable to forensic science?

A

estimate the time of death// through identifying pathogens or toxins// tracking body movement//

58
Q

What are 4 main evidence used within crime scenes around death?

A

PHYSICL - Post-mortem changes / presence of insects // ENVIRONEMNTAL - indoor, outdoor, in water, burnt…/ HISTORICAL- victim habits, daily routines, relationships/ Additional evidence - watches stopped/ phone records…

59
Q

What equation can be use to calculate hours since death.

A

(98.6 degrees F - internal body temperature ) divided by 1.5

60
Q

Name some factors which affect rate of cooling of a body?

A

Size of body/ fat content// position of body (stretched or foetal )// blood loss// environemnt (dry/wet/cold/warm)//

61
Q

What is livor mortis?

A

skin discolouration caused by pooling of blood(blood settles due to gravity , if face down blood migrates to body parts in contact with the floor.)

62
Q

What is algor mortis?

A

cooling of the body

63
Q

What is rigor mortis?

A

stiffening of skeletal muscles/ caused by a reduction of ATP within muscle cells

64
Q

What is mummification?

A

body dries out, water is removed

65
Q

What is apidocere?

A

hydrolysis of body fat resulting in bloating (water replaces body fat)

66
Q

What is Accumulated Degrees Days?

A

the total temperature the body has been exposed to since death/ how many days it has taken the body to reach the level of decomposition identified by TBS(total body score)

67
Q

What is the equation for ADD?

A

10^(0.002 x TBS X TBS + 1.81) +_388.16

68
Q

What are the main stages of decomposition ?

A
  1. FRESH (body cools, rigor mortis) // 2. BLOAT (discolouration, gas accumulates causing swelling) // 3. PUTREFACTION ( tissues liquify, skin blackens, body deflates.) // 4. ADVANCED DECAY( loss of skin and soft tissue)// 5. SKELETONISED (environmental and biological processes lead to complete decomposition of anything but skeleton.)
69
Q

What test can be used to identify alcohol ?

A

EtG test, with a colour change from clear to pink if alcohol is present.

70
Q

What is the test used for testing cannabis?

A

9 - carboxy- 11 nor- delta - 9 THC , turning a yellow precipitate

71
Q

What is the test used to test for arsnic ?

A

DMA, solution becomes a chocolate brown precipitate when present

72
Q

What test can be used to test for succinic acid ?

A

Succinic acid, turns whit perception.

73
Q

What are the two poison which we tested for in the lab?

A

Succinic acid , Arsnic

Contemporary issues in biology 2Y (6 decks)

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