Investigating the Use of Forensic Stylistic and Stylometric Techniques in the Analyses of Authorship

234 Pages·2013·3.09 MB·English

INVESTIGATING THE USE OF FORENSIC STYLISTIC AND STYLOMETRIC TECHNIQUES IN
THE ANALYSES OF AUTHORSHIP ON A PUBLICLY ACCESSIBLE SOCIAL NETWORKING
SITE (FACEBOOK)

by

COLIN SIMON MICHELL

submitted in accordance with the requirements
for the degree of

MASTER OF ARTS

in the subject

LINGUISTICS

at the

UNIVERSITY OF SOUTH AFRICA

SUPERVISOR: PROF EH HUBBARD

JULY 2013
I

Declaration
I declare that “Investigating the use of forensic stylistic and stylometric techniques in the
analysis of authorship on a publicly accessible social networking site (Facebook)” is my
own work and that all sources that I have used or quoted have been indicated and
acknowledged by means of complete references.

Signature:

Colin Simon Michell
[Student No: 4322-607-8]
II

Summary
This research study examines the forensic application of a selection of stylistic and
stylometric techniques in a simulated authorship attribution case involving texts on the
social networking site, Facebook. Eight participants each submitted 2,000 words of self-
authored text from their personal Facebook messages, and one of them submitted an
extra 2,000 words to act as the ‘disputed text’. The texts were analysed in terms of the
first 1,000 words received and then at the 2,000-word level to determine what effect text
length has on the effectiveness of the chosen style markers (keywords, function words,
most frequently occurring words, punctuation, use of digitally mediated communication
features and spelling). It was found that despite accurately identifying the author of the
disputed text at the 1,000-word level, the results were not entirely conclusive but at the
2,000-word level the results were more promising, with certain style markers being
particularly effective.

Key words
Facebook; authorship attribution; style markers; idiolect; forensic linguistics; forensic
stylistics; stylometrics; WordSmith Tools
III

Acknowledgements
I would like to express my thanks to the following:

- All the researchers and experts whose work I consulted.

- Professor Hilton Hubbard for being such a supportive and tolerant supervisor,
who occasionally allowed me to trip over my own feet until I understood what had
to be done.

- The participants who graciously sent me writings from their Facebook inboxes
and allowed me a privileged look into their private worlds.

- My wife Nicola and daughter Roshyin and son Kiyan for all their moral support.

- My previous employers at International House Johannesburg who gave me time
during my work day to visit Pretoria for discussions with Prof. Hubbard, and to my
current employers at the Higher Colleges of Technology - Fujairah for allowing
me the use of their facilities and photocopiers.

Finally, this research is dedicated to my late father John Howard Michell, who always
supported my dreams to better myself, and Roshyin’s twin sister Skylar, who was with
us for such a short time.
IV

Table of Contents

1. Chapter 1 – Aims and Rationale
1.1 Introduction 1
1.2 Research problem 2
1.3 Research Aims 4
1.4 Rationale for the study 5
1.4.1 Introduction to social networking sites 6
1.4.2 Criminal activity on Facebook 15
1.4.2.1 Paedophile activity on Facebook 15
1.4.2.2 Identity theft 16
1.4.2.3 Murder, rape and kidnapping cases 18
1.4.2.4 Cyberbullying 19
1.4.3 Linguistic conventions on social networking sites 20
1.4.3.1 What is digitally mediated communication (DMC)? 20
1.4.3.2 Linguistic implications of digitally mediated communication 21
1.4.3.3 Online anonymity and cryptolects 23
1.4.4 Concluding remarks on the rationale 25
1.5 Research method 26
1.6 Conclusion 27
1.7 Structure of the study 27

2. Chapter 2 – Literature Review
2.1 Introduction 30
2.2 A brief history of forensic linguistics 31
2.3 Stylistics and stylometry within the field of forensic linguistics 33
2.4 The idiolect debate 35
2.4.1 Idiolect and authorship attribution 35
2.4.2 Idiolect and the Unabomber 37
2.4.3 Objections to the importance of idiolect in authorship attribution 37
V

2.5 Language variation 39
2.5.1 Reasons for language variation 39
2.5.2 Language variation in authorship attribution 40
2.6 Language style 41
2.6.1 Spoken and written language 41
2.6.2 Language use in DMC 42
2.6.3 Linguistic norms 43
2.7 Style markers 45
2.7.1 What constitutes a suitable style marker 45
2.7.2 Cautions regarding style markers 46
2.7.3 Some style markers related to the study 47
2.7.3.1 Keywords 48
2.7.3.2 Function words 50
2.7.3.3 Punctuation and spelling 52
2.7.3.4 Most frequently occurring words 56
2.8 Conclusion 57

3. Chapter 3 – Research method
3.1 Introduction 59
3.2 Ethical considerations 60
3.3 The participants in the study 60
3.4 Data collection 61
3.5 Research methods 62
3.6 Qualitative analysis 64
3.6.1 Aspects of a qualitative analysis 64
3.6.2 Markedness in qualitative analysis 66
3.6.3 Mistakes and errors 66
3.7 Stylistic assessment of the participants’ writing 67
3.7.1 Categorisation of stylistic features 67
3.7.2 Descriptors for forensic document analysis 69
VI

3.8 Quantitative analysis 71
3.8.1 Importance of quantitative analysis 71
3.8.2 WordSmith Tools 72
3.8.2.1 Keywords 72
3.8.2.2 Concord 74
3.8.2.3 Wordlist 74
3.8.3 Statistical methods and the Chi-square test 75
3.9 Stylometric analysis of the participants’ writing 77
3.9.1 Test 1: Keywords 78
3.9.2 Test 2: Function words 79
3.9.3 Test 3: Most frequently occurring words 80
3.9.4 Test 4: Punctuation 81
3.10 Conclusion 84

4. Chapter 4 – Findings
4.1 Introduction 86
4.2 Qualitative analysis 86
4.2.1 Writer X 87
4.2.2 Writer A/Writer X 88
4.2.3 Writer B/Writer X 90
4.2.4 Writer C/Writer X 92
4.2.5 Writer D/Writer X 94
4.2.6 Writer E/Writer X 96
4.2.7 Writer F/Writer X 98
4.2.8 Writer G/Writer X 100
4.2.9 Writer H/Writer X 102
4.2.10 Summary of qualitative findings 103
4.3 Quantitative analysis 104
4.3.1 Keywords 104
4.3.1.1 Keywords (1,000-word level) 106
4.3.1.2 Keywords (2,000-word level) 110
VII

4.3.1.3 Keywords conclusion 114
4.3.2 Function words 116
4.3.2.1 Function words (1,000-word level) 116
4.3.2. 2 Function words (2,000-word level) 118
4.3.3 Most frequently occurring words 119
4.3.3.1 Most frequently occurring words (1,000-word level) 119
4.3.3.2 Most frequently occurring words (2,000-word level) 121
4.3.4 Punctuation 123
4.3.4.1 Punctuation (1,000-word level) 123
4.3.4.2 Punctuation (2,000-word level) 125
4.4 Summary of results 127
4.4.1 Qualitative summary (1,000-word level) 127
4.4.2 Qualitative summary (2,000-word level) 128
4.4.3 Quantitative summary (1,000-word level) 129
4.4.4 Quantitative summary (2,000-word level) 130
4.5 Conclusion 130

5. Chapter 5 – Conclusion
5.1 Introduction 135
5.2 Overview of the study 135
5.3 Contributions of the study 139
5.3.1 Facebook language and authorship analysis 139
5.3.2 Stylistic analysis 140
5.3.3 Stylometric analysis 141
5.4 Limitations of the study 144
5.4.1 Style markers 144
5.4.2 Data collected and comparisons made 145
5.5 Suggestions for further research 146
5.5.1 Text analysis of male authors 146
5.5.2 Second language speakers 146
5.5.3 Facebook updates and group threads 147
VIII

5.6 Conclusion 148

6. References 149

7. Appendices
Appendix 1: Permission letter 162
Appendix 2: Request letter 163
Appendix 3: Participants’ texts
1. Writer X 164
2. Writer A 169
3. Writer B 174
4. Writer C 180
5. Writer D 186
6. Writer E 192
7. Writer F 197
8. Writer G 203
9. Writer H 209
Appendix 4: Keyword analysis (1000-word level) 215
Appendix 5: Keyword analysis (2000-word level) 218
IX

List of figures

Chapter 1 – Aims and rationale
Figure 1.1 A standard discussion post resulting from a status update 8
Figure 1.2 Facebook sign-in page 9
Figure 1.3 Example of a friends list 11
Figure 1.4 An example of a Facebook message system 14
Figure 1.5 Typical message left on a user’s 14
Figure 1.6 Typical Instant Message thread 15
Figure 1.7 Part of a chat dialogue between Mr Rutberg, a Facebook friend 17
and the scammer

Chapter 2 – Literature review
Figure 2.1 Google search of “I asked her if I could carry her bags” 36

Chapter 3 – Research method
Figure 3.1 Screenshot from the KeyWord Tool 73
Figure 3.2 Screenshot from the Concord Tool 74
Figure 3.3 Screenshot from the WordList Tool showing the frequency list 75
Figure 3.4 Example of a keyword test 78
Figure 3.5 Example of a wordlist 79
Figure 3.6 Character profiler utility 82
Figure 3.7 Microsoft word search function 83

Chapter 4 – Findings
Figure 4.1 Concordance for ‘cause 101
Figure 4.2 Writer A Keywords 105

Chapter 5 – Conclusion
Figure 5.1 Facebook group thread 147