Forensic Phonetics Dr Erica Gold A-Level Teacher Symposium 20.06.15

Forensic PhoneticsDr Erica Gold

A-Level Teacher Symposium20.06.15

Outline

• Introduction• What is Forensic Phonetics?• What tasks are involved?• Forensic speaker comparison• Case examples• Methodologies• Limitations

Introduction

• Forensics has gained a popular following in recent years with the growth of forensics in popular culture

= ‘CSI Effect’• Positives and negatives of the ‘CSI Effect’

Introduction

• Forensic Science is the term used to describe the processes/methodologies involved in examining/analyzing information that can be used in a court of law or for investigative purposes

What is Forensic Phonetics?

• The use of speech (or phonetics) as evidence or for investigate purposes in the context of the legal system.

• What is phonetics?• A branch of linguistics that is concerned with

the study of human speech/sounds

Phonetics

• Articulatory – the way in which sound(s) are produced

• Acoustic – the physical representation of sound(s)

• Auditory – the perception and reception of sound(s)

Phonetics

• Segmental– Vowels– Consonants

• Suprasegmental– Voice quality– Fundamental frequency (pitch)– Stress– Rhythm

What Tasks are Involved?

• Transcription• Voice Line-Ups• Disputed Utterances• Speaker Profiling• Forensic Speaker Comparison

Transcription

• The transcription of speech and sounds– Often includes elements of speaker attribution

• UK Regulations – require transcriptions done by experts

• Includes time stamps, descriptions of non-speech sounds, notations for inaudible speech, etc.

What Tasks are Involved?

• Transcription• Voice Line-Ups• Disputed Utterances• Speaker Profiling• Forensic Speaker Comparison

Voice Line-Ups/Voice Parade

• Similar to visual, police line-ups except with voices rather than actual faces

• Performed in accordance with the MacFarlane Guidelines (2003)

What Tasks are Involved?

• Transcription• Voice Line-Ups• Disputed Utterances• Speaker Profiling• Forensic Speaker Comparison

Disputed Utterances

• What is (or is not) being said• E.g. Did they say ‘fun’ or ‘gun’?

What Tasks are Involved?

• Transcription• Voice Line-Ups• Disputed Utterances• Speaker Profiling• Forensic Speaker Comparison

Speaker Profiling

• Considering any voice evidence with the aim of deducing who the speaker on a recording may be

• Accent, gender, pathologies, education, idiosyncrasies , etc.

What Tasks are Involved?

• Transcription• Voice Line-Ups• Disputed Utterances• Speaker Profiling• Forensic Speaker Comparison

Forensic Speaker Comparison

• The task of forensic speaker comparison generally involves expert judgment of whether a criminal and suspect recording have come from the same person.

• More specifically - the probability of obtaining the evidence given the prosecution hypothesis, over the probability of obtaining the evidence given the defence hypothesis.

Forensic Speaker Comparison

Conducted an International Survey of Forensic Speaker Comparison Practices in 2011:

• 36 survey participants from 5 continents in 13 countries

• 70% of case work involves forensic speaker comparisons

• 18,221 cases, someone as many as 6,000 in their lifetime

• 2-50 years experience

• 18 - universities or research institutes, 13 - government laboratories/agencies, 9 - private laboratories, and 7 - individuals

Forensic Speaker Comparison

• Analysis:– Auditory– Acoustic– Auditory + Acoustic– Automatic Speaker Recognition– Automatic + Auditory/Acoustic

Case Examples

Conspiracy to blow up the London Stock Exchange and related terrorist charges |In the matter of R -v- Mohammed Chowdhury, Gurukanth Desai, Nazam Hussain, Usman Khan, Omar Latif, Abdul Miah, Mohibur Rahman, Shah Rahman and Mohammed Shahjahan.

Trayvon Martin and George Zimmerman| Murder case in the state of Florida

Case Examples

The Yorkshire Ripper Hoaxer

Plebgate| Altercation between Conservative MP Andrew Mitchell and the police, which took place on 19 September 2012. It gained notoriety for the conduct claimed of Mitchell.

Methodologies

• The UK is largely human-based analysis, but varies in other countries

• The UK approves the expert rather than the evidence• Other countries do the opposite– e.g. USA

• Methods are continually evolving, only started gaining popularity as evidence in the late 1980s

• Need lots more research on specific areas, especially on different accents

Limitations

• Voice is not like other biometric data• Population statistics• Different countries have different rules and

regulations regarding the use of voice evidence (and forensic evidence more generally)

• The presentation of evidence• Judge and jury understanding

Thank You

Questions or Comments?