A new technique for the forensic analysis of text messages may soon be used in court, according to research to be released on Monday at the BA Festival of Science in Liverpool. The technique, which can also be applied to e-mails, chatroom conversations and other electronic messages, makes it possible to determine the likelihood that two messages were written by the same person.
Tim Grant, deputy director of the Centre for Forensic Linguistics at Aston University, described how linguistic analysis is used in police investigations such as the one triggered by the disappearance of Jenny Nicholl in 2005. Analysis of text messages sent from Jenny Nicholl’s phone showed that they were more likely to have been written by murder suspect David Hodgson.
Dr Grant analysed the characteristic abbreviations used in the messages. For example, Jenny Nicholl consistently wrote “I am” and “myself”. The texts sent from her phone after her disappearance instead contained “im” and “meself”, features that were common in messages sent by Hodgson from his own mobile phone. The evidence helped to secure Hodgson’s conviction for murder in February this year.
These techniques have also been applied in the workplace, in cases where employees are suspected of sending malicious e-mails anonymously. “New technologies have created an anti-social phenomenon of mass anonymity. The ability to identify the writer can only be beneficial for society,” said Dr Grant.
Spelling, abbreviations and even the type of message sent can indicate whether a message is likely to have been written by a particular author.
Working with biologist Andrew Price from the University of Warwick, Dr Grant has adapted statistical techniques previously used to measure populations of sharks. The new measures place forensic linguistics on a firmer methodological foundation. “We’re moving from opinion based expertise towards a method that makes it easier to discuss issues like error rates and variance,” he explained.
Dr Grant is already using these techniques to support his analysis of text but in court he still presents extracts from the text. He believes that the new measures must be more widely understood before they can be used as evidence in court cases.
Asked about the possibility of mass screening for suspects using text messages, Dr Grant urged caution and said that other forms of evidence would always be needed to determine likely suspects. The new method is not able to discriminate reliably between large numbers of subjects. Dr Grant stressed that language was much more complex and variable than either DNA or fingerprints.