Texting: Just Like Fingerprints

Ed McBain would be all over this, if he were still around. Lawrence Block probably has a book in the works about it. And Ian Rankin's John Rebus is already a texting fool.

Yes, mobile phone text messaging has moved from college and high-school campuses to criminal investigations, and surely mystery writers can't be far behind.

What led to this was a 2002 murder investigation in the UK where an alibi was broken based on evidence that Stuart Campbell--not the victim Danielle Jones--had sent crucial messages from her phone. Campbell's alibi was broken based on text analyses which revealed that the texts had not been written by Jones, but that they had been faked to deflect suspicion from Campbell. There were a number of differences in the texting styles between the victim and Campbell.

With this background, psychologists at the University of Leicester's Forensic Section of the School of Psychology are investigating texting language to develop more precise techniques for identifying individuals by their texting style. The six-month study will assess similarities and differences in texting style, between texts sent by individuals and within and between networks of people who frequently text one another. The researchers are inviting ordinary people -- murderers need not apply -- to help them with the study by completing an anonymous on-line questionnaire. Although forensic authorship analysis is a growing area of research, this is the first study to focus on mobile phone texting.

The researchers are looking to recruit at least 100 volunteers who will each be asked to contribute 10 text messages. The study is anonymous, so participation is confidential and people have the right to withdraw from the study at any time if they so wish. The texts contributed to the study will be analysed using linguistic and statistical techniques and results submitted to the Journal of Speech Language and the Law.

"We are looking for volunteers to participate in a unique forensic linguistic study, assessing similarities and differences in text messaging style," says forensic linguist Tim Grant who, along with forensic researcher Kim Drake, is conducing the study. "This piece of Leicester research will have important applications for forensic investigation -- for example, in the past text messages have been used as an alibi to murder. Being able to say who wrote a particular text message sent from a particular phone has many potential forensic applications.

"As texting is both a relatively new mode of communication and a particularly informal way of using language, there is not a strong expectation that texters will follow linguistic conventions. This freedom therefore allows for significant individual differences in text messaging style, and this can be used to identify the text's authors. Forensic authorship analysis has also been used in cases involving disputed confession, the sending of abusive or threatening emails or letters and in cases of copyright infringement."

The linguistic analysis will concentrate on individuals' texting strategies and vocabulary; for example, the examples (1)-(4) below show four different texting styles and vocabulary that may be analysed.

1. "Came to see K bumped into B 2."
2. "Shall we get last bus to station"
3. "Pls cn i meet. Tried fonin 4 u."
4. "C U L8R"

According to Grant, individual differences can often be seen by just looking at the text; for example, it is likely that the first two texts were created using a predictive texting function. The reason for this supposition is the resultant word deletions (for example, "Came" rather than "I came" or "get last bus" for "get the last bus") that can be seen in texts 1 and 2. On the other hand, the last two texts use more abbreviated text language with vowel deletions ("Pls"), as well as letter and number homophone substitutions ("C" for "see" and "8" for the middle syllable of "later"). What's important to note is that texting strategies are likely to remain relatively constant within individuals and, along with the actual vocabulary used by an individual, may help identify the writer of a text.

The statistical analyses will use methods developed for linking crimes committed by serial offenders. These methods involve the use of, what are known as, coefficients of similarity (an example of which is the Jaccard's coefficient) which will be used to identify the salient linguistic features of texts by a single individual. That is, it will identify the major differences in the texting strategies and vocabulary across individuals. The same statistical techniques will be applied to identify differences between groups.

Posted by Jon Erickson at 09:18 AM  Permalink