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Analytical Techniques In Forensic Science > Analysis Of Evidence > Flashcards

Analysis Of Evidence Flashcards

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1
Q

What is Evidence?

A

Can be defined as information that is given in a legal investigation, to make a fact or propositions more or less likely.

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2
Q

What are the key forms of evidence in court?

A

Testimonial, documentary and physical, digital, demonstrative

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3
Q

What is testimonial evidence?

A

refers to eyewitness statements made under oath or affirmations

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4
Q

What is a competent witness ?

A

A witness who gives facts about that case as they have the mental capacity to understand the question put to them.

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5
Q

What should competency not be confused with?

A

Credibility and reliability

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6
Q

What are the factors affecting eyewitness testimonies?

A

Weapon focus, internal factors (stress), external factors (leading questions), post event factors (new information)

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7
Q

What are the things to consider about eyewitness testimonies?

A

-type of crime
-how witness saw it
-interviewing techniques used
-time lapse between incident and testimony
-has the witness already identified the suspect or a diffferent individual
-relationship

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8
Q

What is documentary evidence?

A

Any document produced for the inspection by the court as evidence of its contents. It could also be any evidence that contains a record of some kind and builds up the documentation of the events leading to the crime often presented during the trials

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9
Q

What are examples of documentary evidence

A

Diaries,letters,contracts and newspapers

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10
Q

What is physical evidence?

A

Any material item that would be present at the crime scene, on the victim or found in a suspects possession

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11
Q

What form can physical evidence be in?

A

Any form such as small, large, microscopic or odour

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12
Q

When does the role of the forensic science begin ?

A

Begins at the crime scene

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13
Q

What is meant by a crime scene ?

A

Any location that is searched for physical evidence

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14
Q

Do all crimes have a crime scene ?

A

Yes

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15
Q

How many crime scenes can an incident have ?

A

Multiple

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16
Q

What is the order of events for forensic science in a criminal investigation ?

A

-recovery and continuity of evidence
-laboratory work on physical evidence
-interpretation and evaluation of evidence and presentation of findings in court

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17
Q

Who sends evidence for analysis in a lab ?

A

Soco’s

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18
Q

in what form is forensic evidence presented in court ?

A

Expert witness document

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19
Q

What is continuity of evidence ?

A

chronology of who have been responsible for its safekeeping and appropriate handing (chain of custody)

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20
Q

What measures are taken to prevent tampering of evidence ?

A

-tamper-evident seals on evidence packaging
-dedicated secure evidence storage facilities
-secure contemporaneous note taking
-uninterrupted chain of custody
-minimizing the number of people in the chain of custody

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21
Q

What measures are taken to prevent accidental contamination of evidence ?

A

-SOPs that incorporate anti-contamination measures:
-the isolation of bulk and trace evidence
-the use of PPE
-the decontamination of surfaces between samples
-isolation of samples between victims and suspects
-re-packaging every samples as soon as it has been analyzed

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22
Q

What measures are taken to prevent deterioration ?

A

-appropriate packaging and storage
-assiduous logging and note taking

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23
Q

When would evidence be deemed inadmissible ?

A

If continuity of evidence cannot be adequately demonstrated, as the loss of its integrity cannot be ruled out

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24
Q

What is evidential value ?

A

How useful an item is in telling us something

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25
Q

What helps determine evidential value ?

A

-has a crime been committed
-Identity
-link suspect or victim to each other
-establish a connection between different crime scenes
-corroborate or refute evidence from another source

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26
Q

Once the evidence has been analyzed what can the scientist do ?

A

-interpret: ascertain what may be established about the nature of the item
-Evaluate: the data obtained to establish whether it supports the prosecution or defense proposition

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27
Q

What is Streamlined Foresnic Reporting (SFR) ?

A

-multi-step process
-standardised form to report the outcomes of crime scene processing and laboratory analysis to the police, defence, prosecution

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28
Q

How do expert witness statements have to be written ?

A

In layman’s terms and be easily understood by non-scientists within the criminal justice system

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29
Q

What are common types of evidence ?

A

-direct
-circumstantial
-associative
-reconstructive

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30
Q

What is direct evidence ?

A

Eyewitness statements and confessions

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31
Q

What is circumstantial evidence ?

A

Evidence which is inferred from a set of circumstances that relate to the event

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32
Q

What is associative evidence ?

A

Any evidence that ties a suspect to the crime scene, victims or other evidence

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33
Q

What is reconstructive evidence ?

A

Any evidence that allows investigators to gain an understanding of the actions that took place at the scene

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34
Q

What is rebuttal evidence ?

A

Evidence offered to disprove or contradict the evidence presented by an opposing party

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35
Q

What is primary facie evidence ?

A

Evidence that will establish a fact or sustain a judgement unless contradictory evidence is produced

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36
Q

What is exculpatory evidence ?

A

Evidence tending to establish a criminal defendants innocence

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37
Q

What must evidence be for it to be accepted in court ?

A

Relevant and admissible

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38
Q

Whose opinion is accepted as evidence in court ?

A

Expert witness

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39
Q

What are the main categories for physical evidence ?

A

Trace and contact evidence
Biological evidence
Impression evidence
Chemical evidence
Other

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40
Q

How is physical evidence utilised ?

A

-provides a investigative lead for a case
-ties one crime to a similar crime or connects one suspect with another
-corroborates statements from witnesses to or victims of a crime
-the elements of a crime help to determine what will be useful as evidence

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41
Q

What did locard’s exchange principle say ?

A

‘Every contact leaves a trace’

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42
Q

What does the transfer of evidence depend on ?

A

-pressure applied
-number of contacts
-how easily it transfers
-form of evidence
-how much of the item is involved

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43
Q

What does evidence persistence depend on ?

A

-what the evidence is
-location
-environment
-time from transfer to collection
-activity of or around the evidence

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44
Q

What is contamination ?

A

undesired transfer of information between items of evidence

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45
Q

Which type of evidence can be readily transferred ?

A

Trace evidence

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46
Q

What does trace evidence allow provide ?

A

Evidence of association

47
Q

What are the implications of re-transfer ?

A

-great care must be taken to avoid possibly cross-contamination
-the possibility of transfer subsequent to the primary transfer must be taken into account during the interpretation of trace evidence
-trace evidence can be readily lost

48
Q

What is a visual way to present the results of trace evidence analysis to show the occurred transfer ?

A

Transfer diagram

49
Q

What is evidence identification ?

A

The examination of the chemical and physical properties of an object and using them to categorise the object as a Member of a group

50
Q

What is an example of evidence identification ?

A

Deterring that a small coloured chip is automotive paint

51
Q

What does evidence identification help do ?

A

Refine the objects identity and its membership in various groups

52
Q

What are class characteristics ?

A

features that place the item into a specific category

53
Q

What are examples of class characteristics ?

A

-blood type
-make and model of firearms
-shoe print pattern of new shoes

54
Q

What are individual characteristics ?

A

features that distinguish one item from another of the same type

55
Q

What are examples of individual characteristics ?

A

-fingerprints
-strict action marks of fired bullet
-DNA

56
Q

What does individualised mean in terms of evidence identification ?

A

If an object can be classified into a group with only one member

57
Q

What is qualitative analysis ?

A

Information that can provide evidence about the identity of an entity

58
Q

What is Quantitative analysis ?

A

Establish amount or concentration of a substance

59
Q

What is comparison of evidence ?

A

comparison of evidence is done to try and establish the source of evidence. The questioned evidence is compared with objects whose source is known

60
Q

What types of comparison of evidence is there ?

A

-different scenes
-database
-controls
-test impression

61
Q

What is comparison between different scenes ?

A

Comparison between two pieces of evidence obtained from different places

62
Q

Why do forensic scientist compare evidence between different scenes ?

A

To determine whether two pieces of apparently similar forensic evidence may have come from the same source

63
Q

What can comparison between different scenes tell us ?

A

If there is any possible links between the two separate locations from which the evidence has been retrieved

64
Q

What is needed to perform comparative analysis between different scenes ?

A

-2 or more samples
-a questioned and a known sampled

65
Q

What is comparison using databases ?

A

Comparison between an evidential object and a relevant database

66
Q

How are databases used in comparative evidence ?

A

to identify a category to which an item of evidence belongs by establishing its class characteristics

67
Q

What are examples of suing databases ?

A

-bodily fluids or tissues for DNA profiling (nationals DNA database )
-fingerprints (IDENTI)

68
Q

How are controls used in comparative evidence ?

A

Comparison between questioned samples, both positive and negative controls and reference collections

69
Q

What is a questioned sample or unknown ?

A

A sample of unknown origin, usually collected at the crime scene

70
Q

What is a known/ control sample ?

A

A sample of known origin is similar to a positive control sample, which is a known sample used to compare and confirm identity of questioned samples

71
Q

What is a negative control sample/ blank ?

A

A sample used to test the chemical and or equipment for contamination

72
Q

What is a reference collections or standard ?

A

A known sample used to test the chemicals or equipment or to compare with unknown samples

73
Q

How are controls used in comparative evidence ?

A

Comparison between questioned samples, both positive and negative controls and reference collections

74
Q

What are positive and negative controls ?

A

Used to evaluate hypothesis

75
Q

What is an example of an hypothesis ?

A

-suspect is detained and detains a white powder
-hypothesis is that it’s cocaine
-results from the analysis can be compared to the results from the analysis of the known sample (positive control)
-analysis can be carried out without questioned sampled to test for contamination

76
Q

How are test impressions used in comparative evidence ?

A

Comparison between a scene impression and a test impression

77
Q

How are impressions made ?

A

Can be made by recognisable objects such as footwear, tyres and tools

78
Q

What is the general scheme for analysing an item of evidence to determine its potential source ?

A

-collection and preservation of the evidence item
-collection of putative reference source material-known/control
-selection of class and individualising traits from the evidence item
-comparisons of evidence and reference
-common source for evidence and reference or different sources for evidence and reference

79
Q

A t-shirt has stains that look like blood, a test is run that is negative what happens next ?

A

-run a different presumptive test and see if the results change
-run the first test on a sample that is known to be blood that should yield a positive result (positive control )
-run the first test on some fibres from the shirt that have no stains on them (negative control)

80
Q

What three questions does the examiner consider when inferring a common or different source ?

A
  1. Do unexplainable differences exist that convince me that the items compared originate from different sources ?
  2. Do the quantity and quality of the class characteristics convince me that the items could originate from the same source
  3. Do a sufficient number and quality of individualising traits exist to convince me that they originate from the same unique source
81
Q

What is cognition ?

A

the mental process of acquiring knowledge and understanding through thought, experience, and the senses.

82
Q

What do cognitive processes include ?

A

Cognitive processes include mental shortcuts (heuristics), which speed up decision making.

83
Q

What would happen if we didn’t have heuristics ?

A

Decisions would take too long

84
Q

What is a cognitive bias ?

A

is a systematic pattern of deviation from rational judgement and from a strictly objective evaluation of sensory input or data. (Set heuristic)

85
Q

What does an individuals construction of reality do ?

A

dictate their behaviour in the world.

86
Q

What do cognitive biases lead to ?

A

perceptual distortion, inaccurate judgment, illogical interpretation, and decision-making.

87
Q

Why is it important to guard against bias in forensics ?

A

Errors in the process can lead to miscarriages of justice, such as wrongful conviction, traumatic experiences for witnesses or the failure of conviction to convict dangerous perpetrators

88
Q

What is anchoring bias ?

A

the common human tendency to rely too heavily, or “anchor,” on one trait or piece of information when making decisions.

89
Q

What is confirmation bias ?

A

the tendency to search for or interpret information in a way that confirms one’s preconceptions.

90
Q

What is the framing effect ?

A

drawing different conclusions from the same information, depending on how that information is presented.

91
Q

What is status quo bias ?

A

the tendency to like things to stay relatively the same (see also system justification).

92
Q

What is the role effect ?

A

an expert is being engaged by either the prosecution or defence team.

93
Q

What is attentional bias ?

A

implicit cognitive bias defined as the tendency of emotionally dominant stimuli in one’s environment to preferentially draw and hold attention.

94
Q

What is the bandwagon effect ?

A

the tendency to do (or believe) things because many other people do (or believe) the same. Related to groupthink and herd behaviour.

95
Q

What is the reconstructive effect ?

A

when people use what they believe should have occurred to complete gaps in memory.

96
Q

What is the halo effect ?

A

the tendency for a person’s positive or negative traits to “spill over” from one area of their personality to another in others’ perceptions of them.

97
Q

What is false consensus effect ?

A

the tendency for people to overestimate the degree to which others agree with them.

98
Q

What is just-world phenomenon ?

A

the tendency for people to believe that the world is just and therefore people “get what they deserve.” _ similar to victim blaming

99
Q

What led to the error in the Madrid station bombing ?

A

Confirmation bias

100
Q

What’s important for fingerprint analysts that can subject them to cognitive bias

A
  1. Fingerprints from two people can’t be identical but can be similar
  2. Particularly true for latent prints that are smudged or partial so differentiating features aren’t as obvious
  3. The significance of looking at the suspect fingerprint in detail first BEFORE seeing the target for a match is that the analyst would not have focused their observations ONLY on the similarities.
101
Q

What steps could avoid cognitive bias and evidential errors with fingerprints?

A

An important approach in fingerprint analysis is to actively look for any differences, however small, that could exclude two prints from being a match.

102
Q

How many points have to match to confirm an identical fingerprint ?

A

16

103
Q

What was Dror et al’s experiment on ?

A

showed the influence of cognitive bias at the stage of verification or peer review. The source of bias was unnecessary contextual information.

104
Q

What was Dror et al’s method ?

A

-Five experts were asked to re-examine a single pair of prints which had been examined previously in their own caseload.
-All experts had previously judged this pair to be a match.
-However, it was presented to them again as if it were related to the Madrid bomber case, a notorious case of an erroneous identification.

105
Q

What were the results of Dror et al’s study ?

A

Four out of five experts changed their judgement as a result of the contextual information revealed to them. One expert gave the same, correct decision as before.

106
Q

What methods in forensic science are vulnerable to cognitive bias ?

A

-visual observation with the human eye
-fingerprint analysis
-forensic anthropology
-hair and fibre analysis
-blood pattern analysis
-fire investigation

107
Q

When do biases become problematic ?

A

when they narrow down our interpretations too fast, and close off alternative interpretations or solutions.

108
Q

How can cognitive biases relate to one’s scientific training ?

A

By trusting an analytical approach because everyone else does it, even if the underlying scientific rationale or evidence base is weak.

109
Q

What was the Casey report ?

A

Baroness Casey was commissioned to write a detailed report on the current state of the Metropolitan Police in 2023. This was primarily in response to the murder of Sarah Everard by a serving police officer. Her 363-page report concluded that it was ‘institutionally’ racist, misogynistic and homophobic.

110
Q

What is the IOPC ?

A

Independent office for police conduct

111
Q

Why did the IOPC dismiss 6 police officers in 2022 ?

A

For misconduct of sharing offensive messages and failing to challenge, report or condemn offensive views when they were found to share over 6000 messages in a WhatsApp group

112
Q

What strategies are there to overcome bias ?

A

-blinding
-fillers
-Linear sequential unmasking
-case manager model
-peer review/blind verification
-experts’ acknowledgement of their potential for bias (or confronted with evidence of their own bias)
-education and training in cognitive bias

113
Q

What is blinding ?

A

Giving no contextual information

114
Q

What are fillers ?

A

Providing irrelevant evidence

Analytical Techniques In Forensic Science (5 decks)

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