Forensic Linguistics: Investigating linguistic evidence with or without distortions
Forensic linguistics is a branch of applied linguistics, where the accumulated knowledge of theoretical linguistics is applied to the field of forensic investigation in order to interpret linguistic evidence. It is a discipline which is based on the assumption that every person has a unique use of language, which is consistent and cannot be easily altered, almost like a fingerprint, namely the linguistic fingerprint and draws skills from fields such as phonetics, corpus linguistics and sociolinguistics to apply in criminal investigations. (Coulthard et al., 2016) in cases such as trademark disputes, cases for the defense etc. Forensic linguistics has more than often played a decisive role in the investigation of both spoken linguistic evidence such as recordings and written linguistic evidence, such as text messages, even when this evidence was in some way distorted. This paper will present methods in forensic linguistics and the role played by forensic linguistics in the investigation of written and spoken linguistic evidence in two cases where the evidence was corrupt and in two cases where the evidence was incorrupt.
Initially, when it comes to the investigation of written evidence, forensic linguistics is heavily based on the discipline of authorship identification, which according to Nini (2014) is ‘the task of determining information about the background of the author of an anonymous text based on the language of the text’ (p.13). Authorship identification is usually based on the analysis of corpora, which are collections of texts which are stored and processed in a computer in order to serve the purpose of linguistic research. In the investigation of the murder of Amanda Birks, corpus linguistics helped uncover her husband’s plot to murder her through the investigation of text messages, which was what finally led to the conviction of the murderer and in the resolution of the case of the murder of Amanda Birks. (McCarthy and O'Keeffe, 2010)
Amanda and Christopher Birks were a couple who lived along with their son and daughter in Stoke-on-Trent. Christopher was possessively jealous of Amanda until she eventually decided to abandon him for a colleague of hers and after Amanda announced her decision to Christopher, he planned to murder her and set the house on fire to make it appear as Amanda died in the accident. Then on the 16th of January 2009 he strangled Amanda and took possession of her phone to send a text message to her mother, pretending to be Amanda, finally texting that she was going to have an aromatherapy session on the 17th of January, then he proceeded to burning the house with an aromatherapy candle and fled with his children to ask for help. Christopher was claiming that Amanda died in the fire, but the toxicology examination on Amanda’s body showed that she was dead at least 24 hours before the fire and the fibre assessment on the clothes she wearing showed that these were the clothes she was wearing outside the house and not some home clothes she would wear for an aromatherapy session. (Staffordshire Police Authority, 2010) But still, the messages Amanda sent her mother were creating a logical deficit in the case and at this point, thus the legal system turned to authorship identification.
Tim Grant was requested to examine the texts and was provided with the corpus of 407 messages, where 165 out of the text messages were undisputably sent by Amanda Birks and a corpus of 203 text messages those were undisputably written by Christopher Birks until the 17th of January. The police found the messages sent by Amanda Birks after midnight of the 16th of January of 2009 suspicious and Tim Grant isolated them in order to compare them and determine wether they belonged to Amanda or Christopher using corpus linguistics and most specifically, the Wordsmith tools. The Wordsmith Tools is a suite of programs used to identify the behavior of words within a corpus and consists of three main tools: word list, which allows the listing of words according to alphabetical order or frequency, keyword lists, which is a tool used for identifying and locating keywords in a given corpus and finally concord which is a concordance tool which allows users to search for a selected item in the corpus or namely a node, in order to identify the morphology of all words in the data. (Bosseaux,2007) Grant then used the program to identify the stylometric markers of each of the authors, meaning quantifiable markers those would vary among the texts and within the same text, including the frequencies of words and non-words and he excluded elements those appeared less than ten times. More specifically, he noticed that Amanda was texting ‘ad’ for 'had' ‘don’t’ for ‘don’t' which Christopher never used for texting, ‘wud’ for 'would' which was rarely used by Christopher and ‘y’ for ‘yes’, which were somewhat more frequent uses for Christopher as well. Christopher on the other hand was never replacing ‘2’ with ‘to’ with no trailing space and ‘4’ with ‘for’ when writing text messages, which were linguistic behaviors belonging to Amanda and he was rarely using commas and replacing ‘4get’ with ‘forget', which were linguistic behaviours belonging to Amanda. After the above analysis, Grant identified Cristopher as the author of the disputed texts and he finally pleaded guilty and was convicted, Birks’ plot was uncovered and he was sentenced for both Amanda Birks’ murder and for exposing firefighters to dangers since he instructed one of them to enter the house and try to save his already dead wife. (Grant, 2013)
In that case the investigation of written linguistic evidences led a murderer to his punishment, however that type of evidence can be in certain ways distorted or rather, edited by the legal system to distort evidences and lead the courtroom procedures where justice sees fit, such as in the case of Derek Bentley where corpus linguistics would have provided an objective and accurate interpretation of linguistic evidence and could have saved an innocent person from execution and when the actual investigation of the linguistic evidence took place, it was able to grant him a posthumous pardon.
Derek Bentley was a mentally challenged 19 years old man, who along with Chris Craig, his 16 years old accomplice attempted to rob a local warehouse on the 2nd of November in 1952, but were immediately chased by the police. The chase brought the officers along with Bentley and Craig in the rooftops and this point Bentley allegedly uttered an ambiguous sentence ‘let him have it, Chris’ and then Chris Craig began exchanging fire with the police for half an hour until finally killing the Police Constable Sidney Miles, but they were both arrested and were accused of shooting a policeman along with the robbery. The court considered the sentence ’Let him have it Chris’ as a command to Craig Chris to shoot Sidney Miles, because ‘let him have it’ was an expression used by gangsters in Hollywood movies, when commanding shootings while the defence interpreted the utterance as a command to Chris to hand over the gun to the police officer and even Derek Bentley himself disambiguated the utterance with his statement ‘I didn’t know he was going to use the gun’, which unfortunately added to the interpretation of the court that if he was using the article ‘the’, then he was aware of the existence of the gun against him. Finally, the two men were found charged with the murder of a police officer, but since Chris Craig was still underage, he would not be executed but Derek Bentley would be hanged. However, Bentley’s family always defended his innocence and tried to get a pardon for him for years and the second court appeal found further evidence to support Bentley’s innocence.
Some initial considerations expressed at the time of the crime, were that the utterance ‘Let him have it Chris’ presents an inaccuracy to Bentley's idiolect as well, since Bentley never referred to Chris Craig by his actual name but usually called him ‘kid’ or ‘kiddo’ and the utterance was not sufficient to justify the sentence or the initiation of the shooting since Bentley had no place in the shooting and that considering Bentley’s limited mental capacity and lack of education the supposed transcript of his testimony in the police 'I have been cautioned that I need not say anything unless I wish to do so, but whatever I do say will be taken down in writing and may be given in evidence'. does not appear to be accurate to his idiolect and actually appeared similar to police language, giving a lead for linguistic investigation. (Watson, 2016)