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Advanced Forensic Science > Topic 3 - Guideline for Evaluative Reporting > Flashcards

Topic 3 - Guideline for Evaluative Reporting Flashcards

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1
Q

Prosecutors Fallacy

Probability of innocence

A
  • The probability of the proposition given the evidence makes this error.
  • It’s when the probability of innocence given the evidence is wrongly assumed to equal an infinitesimally small probability that that evidence would occur if the defendant was innocent.
  • Highly improbable innocent explanations have led to the assumption of guilt, as with the murder convictions of Sally Clark in 1999 and Lucia de Berk in 2003
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2
Q

Using Bayes Theorem, the prior odds are multiplied by what in order to provide the posterior odds?

A

Likelihood ratio

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3
Q

The level one proposition is known as?

A

Source level

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4
Q

Roy Meadows statistical error was connected with a failure to appreciate —?

A

Conditional Probability

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5
Q

Estabilishing prior odds calculates?

A

Base rate

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6
Q

Evaluative reporting provides

A

It provides ultimately:
* An assessment of the strength to be attached to the findings
* In the context of alleged circumstances

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7
Q

Types of reportiing

A
  1. Evaluative
  2. Intelligence
  3. Investigative
  4. Technical
    Support to the justice system cab be achieved by the production of anyone of these
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8
Q

Hearsay

A

Hearsay is providing information that you didn’t find yourself, you found out through someone else

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9
Q

What conditions have to be met for evaluative reports to be used in court?

A
  1. The forensic practitioner has been asked by a mandating authority or party to examine and/or compare material
  2. The forensic practitioner seeks to evaluate findings with respect to particular competing propositions set by the specific case circumstances or as indicated by the mandating authority
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10
Q

Forensic science findings in court uses probability as a measure of uncertainty. What is the based upon?

A
  1. The findings
  2. Associated data
  3. Expert knowledge
  4. Case specific propositions
  5. Conditioning information
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11
Q

Logically

What does the likelihood ratio measure?

A
  • The likelihood ratio measures the strength of support the findings provide to discriminate between propositions of interest
  • It is scientifically accepted, providing a logically defensible way to deal with inferential reasoning
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12
Q

Likelihood ratio

A
  • The strength of support the findings provide to discriminate between propositions of interest.
  • It provides a numerical scale for findings
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13
Q

How are they key issues in the case established?

A
  1. Considering all available, relevant information
  2. Where necessary, requesting additional information
  3. Agreeing by discussing - when possible or necessary - with the relevant mandating authority
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14
Q

Pre-assessment aims

A
  • Ensures that forensic practitioners consider potential findings before the examination
  • It also helps the identification of the most appropriate examination strategy
  • Specify main potential findings from scientific examinations of the items submitted
  • Assign probabilities (at least within an order of magnitude) for potential findings regarding each proposition
  • This leads to likelihood ratios for potential findings at the assessment stage
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15
Q

If a ‘customer’ directs an examination strategy that , in the opinion of the forensic practitioner, is inappropriate then…

A
  1. Advise accordingly
  2. Make the advice and conversations explicit on the case file
  3. Any resulting limitations on the interpretation[s] shall be described in the report
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16
Q

If access to relevant items is denied or unavailable then…

A

If access to relevant items is denied or unavailable then the mandating authority or party will be advised as to the limits of any resulting interpretation. This advice shall be made clear.

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17
Q

Should be…

Pre-assessment

A
  1. Should be valid and in accordance with an established and controlled methodology.
  2. And made by competent and trained personnel
  3. A likelihood ratio is assigned at assessment stage
  4. The assigned probabilities (at the pre-assessment stage) may be refined in the light of the findings
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18
Q

Four reporting requirements

A
  1. Balance
  2. Logic
  3. Robustness
  4. Transparency
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19
Q

variability,court

What does the regulator say?

A
  1. The current guidance sets out a scientific approach to evaluating observations, based on published research.
  2. It aims to reduce variability in approaches, address the concerns of the courts, increase transparency and adopt a common terminology, which is applicable across the spectrum of forensic science disciplines.
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20
Q

What does the codes of practise stress the importance off?

A

Codes of practice, established by the Forensic Science Regulator stress the importance of an appropriate framework guide the handling of a case from initial receipt of a request through to the provision of evidence in court.

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21
Q

What are the stages of the framework for case management?

A
  1. Reviewing the nature of the expert evidence being requested
  2. Establishing the key issue(s) to be addressed
  3. Determing what examinations and analysis are required
  4. Comissioning those examinations and analyses
  5. Intrepretating the observations
  6. Writing a report
  7. Appearing in court
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22
Q

What should the findings be evaluated with?

A

The findings should be evaluated given at least one pair of propositions
1. Usually one based upon the partys account of the events
2. And one based upon an alternative (opposing partyies) account of the events

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23
Q

What happens if no alternative proposition can be formulated?

A
  1. The value of the findings can’t be assessed
  2. In that case, forensic pratitioners should state clearly that they are not reporting upon the value of the findings.
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24
Q

What should evaluative reports address?

A

The probability of the findings given the proposition and relevant background information

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25
Q

Transposing the conditional

What should evaluative reports not address?

A
  • The probability of the propositions given the findings and background information
  • This can result in transposing the conditional
26
Q

Trace

What should an evaluative report be based upon?

Capable of

A
  • Sound knowledge, experience of the trace type(s) and the use of data.
  • The reporting should be capable of sustaining scrutiny and cross-examination.
27
Q

An evaluative statement will gnerally relate to propositions either at:

A
  1. Sub-source
  2. Source
  3. Activity level
28
Q

Whens should activity level propositions be used?

A

They should be used when expert knowledge is required to consider factors such as:
* Transfer mechanisms
* Persistance
* Background levels of the material which could have an impact on the understanding of scientific findings

29
Q

What conditions affect transfer amounts?

A
  1. The pressure applied during contact
  2. The number of contacts (six contacts between two objects should result in more transferred material than one contact)
  3. How easily the item transfers material (mud transfers more readily than does concrete);
  4. The form of the evidence (solid/particulate, liquid, or gas/aerosol)
  5. How much of the item is involved in the contact (a square inch should transfer less than a square yard of the same material)
30
Q

Direct transfer

A

Evidence that is transferred from a source to a location with no intermediaries is said to have undergone direct transfer; it has transferred from A to B.

31
Q

Indirect transfer

A

Indirect transfer involves one or more intermediate objects-the evidence transfers from A to B to C

32
Q

Indirect transfer

2 points

A
  1. Can become complicated and poses potential limits on interpretation
  2. In almost no cases can a forensic scientist tell the difference between secondary (one intermediary) and tertiary (two intermediaries) transfer
33
Q

Persistence

A
  • Once the evidence transfers, it will remain, or persist, in that location until it further transfers (and, potentially, is lost), degrades until it is unusable or unrecognisable, or is collected as evidence
  • Fingerprints persist longer than fibres so consider this when recovering evidence
34
Q

How long evidence persists depends on:

A

How long evidence persists depends on:
1. What the evidence is (such as hairs, blood, tool marks, accelerants)
2. The location of the evidence
3. The environment around the evidence
4. Time from transfer to collection
5. Activity of or around the evidence location

35
Q

Lukis Anderson

A
  • Lukis Anderson charged with murder he didn’t commit
  • 26-year-old homeless alcoholic with a a long criminal career.
  • The murder victim, Raveesh Kumra, was a 66-year-old investor who lived in Monte Sereno, a Silicon Valley enclave 10 miles away.
  • On Nov. 29, 2012, a group of men broke into Kumra’s 7,000-square-foot mansion.
  • They found him watching TV, tied him, blindfolded him, and gagged him with duct tape.
  • They found his companion, asleep in an upstairs bedroom, hit her on the mouth, and tied her up next to Raveesh.
  • After the men left, the companion, still blindfolded, felt her way to a kitchen phone and called police who arrived, followed by an ambulance.
  • One of the paramedics declared Raveesh dead, suffocated by the duct t tape.
  • Few weeks later, the police arrested Anderson as his DNA had been found on Raveesh’s fingernails.
36
Q

What caused the indirect transfer in the Andersons case?

A
  • Anderson’s DNA was found on the nails of Kumra because, earlier in the day he had been taken by ambulance to hospital.
  • During his treatment he had a finger pulse, oximeter placed on his finger. The same ambulance and oximeter was subsequently used on the deceased.
  • Anderson was in hospitatel due to the consumption of alcohol when Kumra was suffocating
37
Q

Source level propositions

A

Are adequate in cases where there is no risk that the court will misinterpret them in the context of the alleged activities in the case

38
Q

The set of source level propositions can be:

A
  • The bloodstain came from the defendant
  • The bloodstain came from another unknown individual
39
Q

Why would source level be adequate?

A
  • Because particular expert knowledge is not necessary for the court to interpret the findings at activity level
  • because transfer and persistence are not an issue, there is no risk of the report being misleading: the source level information amounts to the activity
40
Q

In cases where the alternative proposition is absent (e.g., one party makes “No comment”), the forensic practitioner can choose one of three options:

A
  1. Adopt alternative propositions
  2. Explote a range of explanations
  3. State the findings, if needed, in a technical report
41
Q

What should you do in the absence of an alternative proposition

Absence of an alternative propositions

A
  • Adopt alternative propositions that most likely and reasonably reflect the party’s position and prepare an evaluative report.
  • Only this option can lead to the production of an evaluative report.
  • The report should specify that any change to the propositions (for example any new propositions proposed by the parties or mandating authority) may impact on the assessment of the strength of the forensic findings.
42
Q

Explore a range of explanations

Absence of an alternative propositions

A

Explore a range of explanations for the findings and prepare, if needed, an investigative report. Provision of such a range of explanations is not an evaluation of the probative source of the findings.

43
Q

State the findings in a technical report

Absence of an alternative proposition

A
  • State the findings, if needed, in a technical report .
  • The report should stress that in the absence of an alternative proposition, it is impossible to evaluate the findings.
44
Q

When the there is an absence of specified propositions, the forensic practitioner should provide:

A

When the there is an absence of specified propositions, the forensic practitioner should provide:
* Intelligence report
* Investigative report
* Technical report

45
Q

In a case in which a considerable quantity of DNA was recovered from the hands of a suspect, and it is alleged that the suspect digitally penetrated a victim…

A

In a case in which a considerable quantity of DNA was recovered from the hands of a suspect, and it is alleged that the suspect digitally penetrated a victim, it is relevant to consider factors such as background and persistence of such trace material; this is particularly so if it is alleged by the suspect that recovered DNA on his fingers is the consequence of a legitimate social contact.

46
Q

R v Weller

Appeal in 2010

A
  • Although the appeal is heard in 2010 the case actually relates to an offence in 2006
  • 30 November 2006 the appellant (Peter Weller) was convicted of sexual assault by penetration
  • Sentenced to three years imprisonment
  • The appellant applied for leave to appeal out of time
  • After several preliminary hearings it was eventually argued that fresh evidence was available on the basis of an expert report.
47
Q

R v Weller

part 33

A
  • Relates to expert evidence and adherence to part 33 of the Criminal Procedure Rules
  • The legal principles are set out in Reed & Reed (2009) which has now be over-ridden
  • Concern the possibility of transfer of DNA material and the ability of experts to evaluate it
  • In particular, where the evidence is not sufficiently reliable for experts to have been able to express and evaluation of the possibilities
48
Q

R v Weller

Factual Evidence

A
  • A 16-year-old female who became drunk at a party
  • The appellant took the victim to bed in order to recover and subsequently inserted his finger into her vagina
  • The victim told the police she had been indecently assaulted

Major part of the DNA mixture is often the victim so you expect more DNA from victim than perpetrator

49
Q

R v Weller

During the evening

A
  • During the evening in question Emma drank very steadily at the party (I)
  • She was violently vomiting in the bathroom having drunk too much (I)
  • It was later agreed she should stay the night so Weller took her to her bedroom and helped her
  • Emma’s evidence was that he returned several times and on one occasion with a bowl in case she vomited again
  • She got into bed as she felt dizzy and unwell (I)
  • She says that Weller began to stroke her body, her breasts and her legs and had then inserted his finger into her vagina (Hp)
  • Her evidence was that she was too shocked to say or do anything, but later got herself together

He Weller said no comment then a proxy proposition would have to be used

50
Q

R vs Weller

Weller’s account

A
  • He helped the victim into bed when she began to vomit (Hd)
  • Whilst in bed he had checked upon her several times and on one occasion had put her into the recovery position (Hd)
  • He had picked up her clothes including her knickers which she had left on the floor (Hd)
  • He strongly denied the accounts of sexual assault that she had given (Hd)
51
Q

R v Weller

Expert evidence (1)

A
  • Focussed upon the Dr who examined the victim (E)
  • This evidence included injuries to the victim’s fourchette and abrasions
  • The injuries were not accidental and had not been caused by infection but because something blunt had penetrated her vagina
  • Fingers were the likely cause of those injuries (E)
52
Q

R v Weller

Expert evidence (2)

A
  • DNA profile (E)
  • The major profile was that of the appellant with a minor components belonging to the victim
  • No challenge was made concerning the collection and analysis of DNA
53
Q

R v Weller

Possibilities of transfer

A

Appeal sets out four possibilities – namely:
* From Weller’s contact with Emma’s hair (Pr)
* Touching Emma when putting her to bed or holding her in the recovery position (Pr)
* Contact with vomit (Pr)
* Inserting his fingers into her vagina (Pr)

54
Q

What are likelihood ratios based off?

A
  • Likelihood ratios are based on the assignment of the probability of the findings given each of the competing propositions.
  • Relevant and appropriate published data will be used wherever possible.
  • If appropriate published data are not available then data from unpublished sources may be used.
  • Regardless of the existence of sources (published or not) of numerical data, personal data such as experience in similar cases and peer consultations may be used, provided that the forensic practitioner can justify the use of such data.
55
Q

What happens if a likelihood cannot be assigned?

A
  • If a likelihood ratio cannot be assigned by the forensic practitioner (due to a lack of knowledge for example), then no appropriate evaluative assessment of the findings can be made.
  • However, likelihood ratios can be informed by subjective probabilities using expert knowledge.
56
Q

Qualitative

Guideline 15 of the Forensic Science Regulators Guidance

A
  • Qualitative evaluations should only be presented as investigative opinions, for intelligence purposes rather than evaluative opinions.
  • They should not be conveyed in a way that the investigator could consider them to have evidential weight.
  • This can only be determined if a statistical calculation can be progressed.
57
Q

What are the two broad forms of evidence / reporting?

A

Categorical and evaluative

58
Q

Mandating authority

A

Mandating authority is the authority that commissions the work (Police, CPS, Border force, etc)

59
Q

R v William Francis Jones

Facts

A
  • That high level of DNA, from the defendant was detected on the firing pin of a grenade.
  • The defendant gave a no comment interview apart from denying handling the item.
  • The expert opinion was that the DNA findings were within the range of expectation, if he had contact with it.
  • The joint report stated that it was not reasonable to expect anyone to be able to account for the way their DNA could have been transferred
60
Q

R v William Francis Jones

Ruling

A
  • Geographical location did not assist in distinguishing between direct or indirect transfer.
  • No conclusion could be reached re-the likelihood of direct or indirect transfer.
  • Direct transfer more probable than indirect transfer – height of the evidence of probability not sufficient for the finding of guilt.
  • The evidence could not be supported by s34 CJPO Act direction
61
Q

What is prosecutors fallacy / when does it occur?

A
  • The prosecutor’s fallacy is a logical fallacy that occurs when a prosecutor presents a statistic as if it represents the probability of guilt, when it actually represents the probability of the evidence given that the defendant is guiltyor innocent.
  • In other words, it’s the mistake of confusing the probability of A given B with the probability of B given A.

Advanced Forensic Science (6 decks)

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