Top Banner
Kristy Martire Senior Lecturer & ARC DECRA Fellow School of Psychology, UNSW JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE
26

JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Dec 07, 2021

Download

Documents

dariahiddleston
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Kristy Martire

Senior Lecturer & ARC DECRA Fellow

School of Psychology, UNSW

JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Page 2: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Expert Evaluative Opinions

Shoe impressions

Fingerprints

Bullets

Handwriting

FORENSIC SCIENCE EXPERTS

Page 3: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

LIKELIHOOD RATIOS

‘There is a critical need in

most fields of forensic

science to raise the

standards for reporting and testifying about the results

of investigations.’

Page 4: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

LIKELIHOOD RATIOS

“…In my opinion, the correspondence between the

footwear mark at the crime scene and the shoe of the

accused is 4.5 times more likely to occur when the

prosecutions version of the crime is correct than when the

defense’s version of the crime is correct.”

Use of likelihood ratios (and verbal equivalents) as the most

scientifically and logically acceptable means of communication.

European Network of Forensic Science Institutes

Page 5: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

McQuiston-Surrett & Saks, 2008

86

75.6

57.4

70.7

0 20 40 60 80 100

Strength

VERBAL EXPRESSIONS OF UNCERTAINTY

Reasonable Scientific

Certainty

Probable

Consistent (with)

Match

MATCH : Some concordance, some similarity, but no

expression of specificity intended; generally

similar but true for a large percentage of the

population

Page 6: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

ASSOCIATION OF FORENSIC SCIENCE PROVIDERS

Likelihood Ratio Verbal Translation (support)

>1-10 Weak or limited

10-100 Moderate

100-1,000 Moderately strong

1,000-10,000 Strong

10,000-1,000,000 Very strong

>1,000,000 Extremely strong

Page 7: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

NUMERICAL EXPRESSIONS OF UNCERTAINTY

Page 8: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

UNDERSTANDING PROBABILITIES

Gigerenzer, Hertwig, Van Den Brock, Fasolo, & Katsikopoulous, 2005

What does

“There is a 30% chance of rain tomorrow”

convey?

It will rain tomorrow for 30% of the time

It will rain tomorrow in 30% of the region

It will rain on 30% of the days like tomorrow

Page 9: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

New

York

67%

Milan

21%

Athens

37%

37%Amsterdam

Berlin

35%

Gigerenzer, Hertwig, Van Den Brock, Fasolo, & Katsikopoulous, 2005World Map By Frank Bennett [Public domain], via Wikimedia Commons

UNDERSTANDING PROBABILITIES

Percent with correct answer ‘c – Days’

Page 10: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

CLEAR COMMUNICATION

Opinions should be expressed

in simple, precise and

unambiguous terms

Page 11: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

1HUNDRED

times more likely

Page 12: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

10THOUSAND

times more likely

Page 13: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

1MILLION

times more likely

Page 14: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Very Strong Support

Strong Support

Page 15: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

How many times?

More likely to be

guilty or not guilty?

Present expert

evidence

How many times?

More likely to be

guilty or not guilty?

Case facts

RESEARCH APPROACH

Prior belief

Posterior belief

Belief change

difference

Page 16: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Likelihood Ratio Verbal Translation (support)

>1-10 [4.5] Weak or limited

10-100 Moderate

100-1,000 [450] Moderately strong

1,000-10,000 Strong

10,000-1,000,000 [405,000]

Very strong

>1,000,000 Extremely strong

EXPERIMENT 1.

Page 17: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

1.33

1.18

0.75

0.1 1 10 100 1000 10000 100000 1000000

Likelihood Ratio

Observed Expected

EXPERIMENT 1 – VERBAL EXPRESSIONS.

Moderately Strong

Very Strong

Martire, Kemp, Watkins, Sayle & Newell, 2013

Weak or limited

Page 18: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

61%

39%

EXPERIMENT 1.

Weak or limitedsupport

by feint PRAISE

is that the BEST

Page 19: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Martire, Kemp, Sayle & Newell, 2014

EXPERIMENT 3.

Present expert

evidence

In favour of

hypothesis 2

(the two fingerprints

originated from

different people).

In favour of

hypothesis 1

(the two fingerprints

originated from the

same people).

Neutral

(No support for

either hypothesis).

x

Page 20: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

EXPERIMENT 4.

Best substitute?

Present Expression

WEAK

55%STRONG

90%

MODERATELY

STRONG

75%

VERY

STRONG

95%

EXTREMELY

STRONG

95%

MODERATE

65%

50% support for A compared to B 100%

What is the best substitute for “weak

support”?

Page 21: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Aitken et. al, Science & Justice 2011

POSITION STATEMENT

5. A verbal scale based on the

notion of the likelihood ratio is

the most appropriate basis for

communication of evaluative

expert opinion to the court

Page 22: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

POSITION STATEMENT

But what about just using the

numbers?

Page 23: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

POSITION STATEMENT

“Numerical likelihood ratios are the

preferred form of communication of

evaluative expert opinions, especially

where there is data to assign a

likelihood ratio through numerical

methods”

CEH Berger (2013)Personal Communication

Page 24: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Likelihood of source?

Present Expression

EXPERIMENT 5.

“99.9375%

WILL NOT

share”

“1 in 1600

WILL

share”

Aytugrul v The Queen [2012] HCA 15

91.2% chance

71.5% chance

What is the likelihood that the defendant was the source of the DNA

from the crime scene?

Page 25: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

3

Probabilistic evidence is challenging

Presentation format does matter

Evidence does not always mean the same thing to everyone

Consultation and collaboration is required

TAKE HOME MESSAGE

Page 26: JURIES & THEIR UNDERSTANDING OF EXPERT EVIDENCE

Contact: [email protected]