Cognitive Bias and Forensic Anthropology

220 Pages·2017·1.96 MB·English

Cognitive Bias and Forensic Anthropology: The Power of Context in
the Interpretation of Skeletal Remains

Sherry Nakhaeizadeh

University College London
Ph.D. Forensic Science
April 2017
Declaration
I, Sherry Nakhaeizadeh confirm that the work presented in this thesis is my own.
Where information has been derived from other sources, I confirm that this has been
indicated in the thesis.

Signed

Date

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In loving memory of my dearest stepmom Maryam, who started this journey with me.
Her love, support, and tremendous courage made me feel that anything is possible.
I carry you in my heart always. I hope I made you proud.

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Acknowledgments
This research was funded by the Engineering and Physical Sciences Research
Council of the U.K. (EPSRC), through the Security Science Doctoral Research
Training Centre (UCL SECReT) based at University College London
(EP/G037264/1).
I wish to thank and express my appreciation to my supervisors Dr Ruth Morgan, Dr
Itiel Dror, and Dr Carolyn Rando for their support, encouragement, and expertise
throughout the process. This thesis was made possible through their guidance and
academic input.
For the love and support provided by my family, Mum, Melinda, Sanaz, Sahar,
Sepideh: Thank you for always believing in me, I will always be grateful.
Special thanks are extended to Nathalie Dozzi for her devoted friendship and
encouragement throughout this process, Nadine Smit, for her guidance, and our
endless thought-provoking discussions, and to all the participants that took their
personal time to participate in my experimental studies.
Last, but certainly not least, Tom thank you for your patience, love, and
unconditional support.

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Abstract
The central role of human cognition in forensic science and its effect on the
interpretation of forensic evidence is being increasingly recognised within the
forensic disciplines. It is clear that the concerns over expert decision-making and
their vulnerabilities have not only been highlighted in recent key governmental
reports, but also created a debate within the literature. This has, within recent years
lead to a rise of empirical research focusing on the impact of cognitive biases in all
stages of the forensic science process, highlighting that these vulnerabilities are not
limited to a specific area of expertise.
In forensic anthropology, the presence of cognitive bias, its impact, and how to
mitigate its effects are still not fully empirically assessed or appreciated. This thesis
seeks to unearth and understand the degree to which contextual biases are present in
forensic anthropology, and present ways that can mitigate the impacts in biological
profiling. This research addresses the effect of context within forensic
anthropological analysis throughout the forensic science process (collection,
analysis, interpretation,) through a series of experimental studies. The results of the
experimental studies showed that context could have a powerful effect in visual
assessments of skeletal remains in sex, ancestry and age at death. Furthermore, the
findings also provided an important first step towards understanding the potential
effects of initial exposure to irrelevant context at a crime scene in the excavations of
skeletal remains, showing a potential for cascading bias on the subsequent
assessment of the skeletal remains.
An evidence-based approach for dealing with cognitive interpretation issues within
the human identification field is presented. The findings of this thesis have
contributed to the body of knowledge and provide empirical data that illustrate the
benefits of developing a more holistic approach to forensic decision-making from
crime scene to court within forensic anthropology and the wider forensic disciplines.

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Table of Content
Chapter 1. Introduction 13
1.1. Overview 13
1.2. Aim and Research Questions 15
1.3. Structure of the thesis 16
1.4. Additional considerations 19
Chapter 2. Literature Review 20
2.1. Human Cognition 20
2.1.1. Schema and Cognitive Bias 20
2.1.2. Heuristics 21
2.1.3. Confirmation Bias 22
2.1.4. Sources and Fuels of Confirmation Bias 23
2.1.5. Belief Perseverance 24
2.1.6. Observer Effect and Contextual Biases 25
2.1.7. Human Memory 26
2.1.8. Cognitive Bias and the Legal System 27
2.1.9. Miscarriage of Justice 29
2.2. The Role of Forensic Science in the Criminal Process 30
2.2.1. Forensic Science and Expert Evidence 31
2.2.2. Expert Evidence Standards in the United States 31
2.2.3. Expert Evidence Standards in the United Kingdom 33
2.2.4. Cognitive Bias and Forensic Experts 34
2.2.5. Cognitive Bias and Research in Forensic Science 37
2.2.6. Cognitive Bias and Casework 39
2.2.7. Addressing Cognitive Bias in Forensic Science and Criminal
Investigations 40
2.2.8. The Legal System 40
2.2.9. Case Manager Model 41
2.2.10. Laboratory 42
2.3. Forensic Anthropology 45
2.3.1. The Biological Profile 46
2.3.2. Human/ Non-Human 47
2.3.3. Sex assessment 47
2.3.4. Ancestry assessments 50
2.3.5. Age at Death 52
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2.3.6. Cognitive Research in Forensic Anthropology 55
2.3.7. Empirical research in Cognitive Bias in Forensic Anthropology 56
2.3.8. Future directions 59
2.4. Aims and Objectives 61
Chapter 3. Cognitive and Contextual Influences in Forensic Anthropology: the
implication of observer effect in biological profiling (Experiment 1 and 2) 62
3.1. Introduction 62
3.2. Methodology 63
3.2.1. Experimental Design 64
3.2.2. Materials 65
3.2.3. The contextual information 66
3.2.4. Participants 67
3.2.5. Procedure 68
3.2.6. Analysis 69
3.3. Results 70
3.3.1. Experiment 1 70
3.3.2. Experiment 2 74
3.3.3. Comparing confidence level 92
3.4. Discussion 95
3.4.1. Experiment 1 (Pilot study) 95
3.4.2. Experiment 2 (Control/follow up study) 97
3.5. Conclusion 102
Chapter 4. Initial exposure to extraneous factors at the crime scene and
subsequent bias in the processing of skeletal remains. 103
4.1. Introduction 103
4.2. Methodology 105
4.2.1. Experimental design 105
4.2.2. Material 105
4.2.3. Participants 107
4.2.4. Procedure 108
4.2.5. Analysis 111
4.3. Results 112
4.3.1. Decisions of all three groups 112
4.3.2. Chi- Square and Fisher Exact test comparing groups in sex
assessment 112
4.3.3. Confidence level of participants 114
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4.3.4. Decision-making change of participants in Control group after
context 115
4.4. Discussion 115
4.5. Conclusion 119
Chapter 5. The order of examination on skeletal remains and cognitive bias 120
5.1. Introduction 120
5.2. Methodology 122
5.2.1. Experimental design 122
5.2.2. Material 122
5.2.3. Participants 124
5.2.4. Procedure 125
5.2.5. Analysis 125
5.3. Results 126
5.3.1. Participants decision-making on the Skull and the Os coxa 126
5.3.2. Chi-square test comparing final sex assessment for Group 1 and
Group 2 127
5.3.3. Independent samples t-test Os coxa 128
5.3.4. Independent samples t-test Skull 128
5.3.5. Independent samples t-test final assessment for Group 1 and Group
2 129
5.4. Discussion 129
5.5. Conclusion 132
Chapter 6. Discussion 133
6.1. Visual assessments and contextual effects 133
6.2. Initial exposure to context at a crime scene 136
6.3. Procedural practice and contextual influences 139
6.4. Contextual effects in forensic anthropology 139
6.5. The culture of error and research in forensic science and forensic
anthropology 143
6.6. Future directions 145
Chapter 7. Conclusion 150
7.1. Summary of the thesis aim and research questions 150
7.2. Research question 1. Does contextual information affect previous
judgments when assessing skeletal remains of an ambiguous nature? 150
7.3. Research question 2. Does early exposure to ‘extraneous’ contexts in
the excavation of skeletal remains cascade and thereby affect the subsequent
assessment of the skeletal analysis? 151
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7.4. Research question 3. Does the order of examination of skeletal remains
a) influence the interpretation of the subsequent skeletal element, and b) act
as an influence and determine the final conclusion of the assessment? 153
7.5. Contribution to the body of knowledge within Forensic anthropology
and Forensic science 153
7.6. Avenues for future research 155

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List of Tables
Table 3.1 Time table of the research design 65
Table 3.2 showing the distribution of all decisions being made for each skeletal
element 70
Table 3.3 showing descriptive information for each decision category 71
Table 3.4 showing the distribution of all decisions being made for each skeletal
element 75
Table 3.5 showing Chi-square and Fisher’s exact test results for all three skulls 90
Table 3.6 showing Chi-square test results for all three skulls 91
Table 3.7 An overall summary of the mean confidence value across all skeletal
elements between all three groups 92
Table 4.1 showing the neutral artifacts associated with each burial 106
Table 4.2 showing the results of the Chi-square and Fisher’s exact test for sex
assessments for all groups compared 114
Table 4.3 An overall summary of the mean confidence value across all groups 115
Table 5.1 showing background summaries and demographic for the participants 126
Table 5.2 An overall summary of the mean confidence value across the skeletal
elements for each group 129

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