24 Jul 2013

Forensic Linguistics: Words on Trial

Nowadays, the word forensic reflects an image of a quirky scientist, a medical examiner and a team of very good looking investigators on a “C.S.I.” show. However, in the real world there are many people that work hard to solve crimes and deliver, for instance Forensic Linguists.

Forensic Linguistics refers to the application of linguistic knowledge, methods and insights to the forensic context of law, language, crime investigation, trial, and judicial procedure. Linguistics is the scientific, systematic study of language. Forensic Linguistics has been designed to meet a growing demand for advanced training in scientific language analysis.

In any criminal investigation where the perpetrator writes an original document, law enforcement can turn to Forensic Linguists to analyse the writing. They can then compare documents written by suspects to that of the perpetrator to determine whether they were written by the same author or someone else. This is possible because even among people that write and speak the same language, every person uses language differently. Each person has his or her own idiolect, i.e. their own personal variety of the language.

In some instances, the personal language can be so unique that Forensic Linguists can say that two documents belong to the same author, because he or she uses a certain word or phrase or has a different writing style to other people speaking the same dialect.

The term was first coined in the 1960s during the analysis of criminal statements. Forensic Linguists can work in the following fields: Forensic Phonetics (voice recognition and identification, which means matching voices of, for instance, a threatening voice on a phone call to a suspect), Linguistic Dialectology (determination through language of where a person is from, has lived or was educated) and Discourse Analysis (study of spoken and written conversation). Forensic Linguists also analyse suicide letters and emergency calls in regards to tone, speed or hesitation and threat communication.

However, Forensic Linguists do not always deal with criminals. Last week it was revealed that the author of a new crime novel The Cuckoo’s Calling was not Robert Galbraith as stated, but the best-selling author J.K. Rowling. With the help of computers and sophisticated statistical analyses, two Forensic Linguists analysed words that carry personal information that one might not realise they provide.

“There’s a kind of fascination with the thought that a computer sleuth can discover things that are hidden there in the text. Things about the style of the writing that the reader can’t detect and the author can’t do anything about, a kind of signature or DNA or fingerprint of the way they write,” says Peter Millican of Oxford University, one of the experts in this field.

The two linguists compared not only features such as word, sentence and paragraph length, letter and punctuation frequency and word usage, but also tested “character n-grams”, i.e. the sequences of adjacent characters (for instance: a search on 4-grams would not only discover jump, but also jumpsjumped and jumping).

The following is a sample case from Professor Malcolm Coulthard, Professor of Forensic Linguistics, Director of the Centre for Forensic Linguistics at Aston University, Emeritus Professor of English Language and Linguistics at Birmingham University, Honorary Professor at Cardiff University:

“A 19-year-old woman went out one Friday evening telling her parents she would be spending the night with friends. On the following Monday she was reported missing after she failed to turn up to work. Her car was found in a pub car park, her mobile phone was switched off, her bank account untouched. Ten days later two friends received text messages saying she had left home to live in Scotland with her (unnamed) boyfriend – no known boyfriend was missing. Five days later her father received two text messages saying she had left home because of her poor relationship with him and her mother.

The police discovered she had been having a relationship for four years with the middle-aged father of one of her friends but had, in the week she disappeared, spent the night at his brother’s flat. Some time later some of her personal effects were found in the local woods close to where she used to go camping with her lover. He became a suspect in her disappearance and I was asked to examine the four text messages to see whether it was likely that she had indeed sent them or, if not, whether the lover might have.

The Police recovered eleven messages she had previously sent to the two friends and over 100 sent by the lover to various friends and relatives. The four suspect messages contained a series of choices words which differed from those in the known text messages. They concluded that it was unlikely that she had texted the messages sent the texts. The lover’s texts contained examples of many, though not all, of the distinctive features, including two spelling mistakes. So they concluded that he was one of a small number of possible authors.

Other evidence about the location of the phone when the messages were sent, the fact that the lover had hired cars on the two days when the messages were sent delivered and the mileage and sighting times were consistent with him having travelled to the locations to send the messages all supported the hypothesis that he had indeed sent the messages was responsible for sending the messages. Putting together all the evidence in the case, of which the texting was a small but important vital part, the jury convicted the lover of murder.”

He is currently appealing.

 



 
 

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