Today I’m on holiday and today this story broke – Bernadette Walker: Scott Walker guilty of murder – BBC News. And this is a fuller version from the Peterborough Telegraph. I knew the verdict was coming, I hoped it was coming, and yet it’s been getting me down.

Once again a man has abused and then killed a young woman and once again that man is a member of the woman’s family.  But this case is unusual. 

In this case, the case of the murder of Bernadette Walker, this man who abused and killed his stepdaughter has been brought to justice.  Scott Walker has been convicted of Bernadette’s murder, in spite of the fact that Bernadette’s body has not been found.  Both Scott and Bernadette’s mother, Sarah Walker, have also been found guilty of perverting the course of justice, in part for sending messages from Bernadettte’s phone, which suggested that she was alive after Bernadette had been killed.   

This was the small part we played in this case. I worked with Márton Petykó to provide an expert report to the police. Our evidence concluded that the messages were inconsistent with Bernadette’s texting, and consistent with either or both of Scott and Sarah. (We couldn’t reliably separate their styles from one another). Sarah Walker admitted sending these messages before the trial. The jury today found that Scott was also guilty of perverting the course of justice with regard to sending these messages and they decided that Sarah must have known or believed that Bernadette was dead, which she had denied. As some of our evidence was agreed and some was less important to the overall case, the prosecutors decided there was no need for our evidence to be put before the jury, and so we didn’t give evidence in person.

This then is justice working.  This is what is meant to happen.  Individuals are held accountable and punished.  We made our limited contribution to the process.  Sentencing will occur in September – Scott will receive a mandatory life sentence for murder, and the judge will have to decide both on Scott’s minimum term in prison and on Sarah’s sentence for perverting the course of justice.  And as we played a small part in this case. I should feel good about this.  But I don’t. I feel depressed and weary.

Forensic linguistics is sometimes defined as a list of topics, or applications, or practices – but I prefer functional definitions.  My definition for forensic linguistics is that it is an attempt to improve the delivery of justice using the analysis of language.  This definition allows a broad focus, including improving legal and judicial processes, improving access to justice, and also  addressing investigative linguistic tasks like we did in this case.

In a small way in this case we have improved, or helped to ensure, the delivery of justice – so that’s good.  It’s also clearly inadequate.  

Criminologists sometimes write about five functions of sentencing, most often when discussing prison sentences. These five functions are punishment, prevention, rehabilitation, restoration and deterrence.

Scott and Sarah Walker, with their convictions and sentences are being punished and prevented from doing further harm whilst in prison, there is also some moderate hope that they will be rehabilitated, to prevent further crimes. 

Restoration though? Bernadette doesn’t get her life back, all those opportunities for friendships, and love and laughter. The opportunity for learning that there are good things in life.  These can’t be given back. That can’t be done. There is no sentence that can bring restorative justice for Bernadette. 

Deterrence seems like an easy target to hit but if we look around we see it really isn’t. Although there are many successful convictions, the violence continues.  Particularly violence against women.  This may be because even as increasing numbers of women are being abused by men (Women’s Aid stats suggest 1.6M domestic abuse cases a year in the UK and rising) most cases of abuse do not result in charge, let alone in conviction. In contrast and thankfully, most murder cases are solved – there’s a roughly 80% conviction rate in murder trials. I’ve not done the proper research today, but media reports suggest that there are currently about 2600 unsolved murders in the UK (some stretching back decades) and that the great majority of victims in these unsolved cases are also women.  

It seems to me that deterrence is failing because of a lack of recognition of the links between our misogynistic culture and the abuse and murder of women. The misogynistic culture we live and breathe, online and off, is all-pervasive and feeds the statistics of violence and abuse.  Rather than thinking about deterrence we need improvement of justice at this social level – today (in my weary and depressed mood) it seems that social justice in this sense is deteriorating. Improvement seems non-existent or at best imperceptible.  The scale of the required change is daunting.  I don’t know how you would measure such a change. Today at least I don’t know how you would target it, or who needs to do it, or even what insights and knowledge are required to make changes at a level and scale that would make any difference. I do know we need to figure this out and we need to do more.

I applaud all those who have achieved the delivery of justice in the Bernadette Walker case. Bringing these convictions was a difficult task and a task that was ultimately done well. For those who work day-in and day-out on such cases – I don’t know how you do it. I’ve probably been working on cases like this for too long, but I do so only occasionally and on days like today it exhausts me. My feeling today at least about the convictions in this case – the contribution to the delivery of justice that these convictions represent – is that both it is to be applauded and also that it is simply not enough.

[minor tweaks, updates and additional link 27th July]

The big reveal in the season finale of Line of Duty was that it was a forensic linguist, who identified ‘H’ aka “the Fourth man” not as some criminal mastermind, but as the bumbling and over-promoted DI Ian Buckells.  The TV police drama has followed the incremental investigations of anti-corruption unit AC12 of the fictional Central Police.  Over the course of six series AC12 has established links between Organised Crime Groups and institutionalised police corruption, and in doing so it has traded on a tension between procedural hyper-realism and credulity-stretching flights of fancy.  The final message of the final episode appears to be that competence can become an ethics issue.  Buckells was no Moriarty, his corruption arose from inability, or lack of enthusiasm in doing his job well.  It was disappointing therefore that the culmination of AC12’s investigation relied on the evidence of a less than competent forensic linguist.

The linguistic plot-twist of the show rested on the spelling “definately” in the communications from the anonymous H. This misspelling had been flagged in an earlier series where we saw Superintendent Ted Hastings, use “definately” in an online chat, in which he assumed the linguistic identity of H.  H was discovered by searching though police files for this misspelling, and in the final interview scene a report is produced from a forensic linguist, that declares H is in fact DI Buckells. 

Each of these events relate to tasks which have been researched by forensic linguists.  Research in linguistic identity assumption shows that identifying lower-level linguistic features such as spelling patterns are necessary to successfully takeover someone’s identity in an online chat, but they are not enough.  Unless Hastings is also able to copy H’s linguistic turn taking and topic control, he is more likely to be discovered.  This is difficult but can be trained.  Our experiments with trainee undercover online officers showed that forensic linguistic training reduced detections by suspicious interactants from about 75% to 25%.  A further issue for Hastings is that he needs to avoid linguistic leakage of his own identity. He would be wise not to drop in the phrase “Mother of God” when chatting as ‘H’.

Using language style as a basis of an author search is also subject to intensive research.  One focus is to use writings by offenders in darkweb fora as a basis for searching for an individual’s writings on the open web.  Author search was used in this way as one of many techniques in the investigation that identified Matthew Falder, one of the UKs worst online sexual abusers. Another example is that the single-word greeting “Hiyas” contributed to the identification of paedophile, Shannon McCoole.  Searching written style in a fairly small collection of police files is significantly easier than searching all of the Internet.

It is the comparative authorship analysis task in Line of Duty , that is perhaps most known application of forensic linguistics, and in the real world this is a task that can and does produce evidence that is taken to court.  The dialogue of Buckells’ investigative interview in Line of Duty would have us believe such evidence can be very strong. Buckells is told that on the basis of the spelling “definately”, and a brief mention of some syntax features, that AC12s forensic linguist “concludes there is a 95% probability the messages detected on GGM-13 were written by you.” This is of itself a red flag suggesting that AC12s forensic linguist is either incompetent or perhaps, for reasons unknown, framing Buckells to take the hit.  

The tell that this is an inept or perhaps bent forensic linguist is the cited 95% probability.  This is not only bad forensic linguistics, it is also poor forensic science.  Contemporary research in forensic science suggests that identification evidence as should not be provided as a conclusion of match or non-match, even with a mitigating probability score.  Such an expression of the result is both  logically incorrect and usurps the role of the jury.  It is the job of the forensic scientist to express the weight of their evidence, and this is best achieved by taking a competing hypothesis approach.  In AC12s case we can easily create the two competing hypotheses with regard to the spelling “definately”.  These would be expressed as 

1. “the probability of seeing “definately” given the hypothesis that Buckells wrote the ‘H’ messages; and,
2.  the probability of seeing “definately” given the hypothesis that anyone else wrote the ‘H’ messages.

To calculate the probability for the first hypothesis you might trawl through all of Buckells’ and H’s writings to come up with a rate of occurrence per thousand words for each of them.  This gives some measure of similarity between Buckell’s and H’s writings in this regard.  But similarity is not enough.  To calculate the probability of the second hypothesis we need to research some base-rate information.  This is where things get tricky.  A quick google search gives me nearly 16,000,000 hits for the spelling “definately” and it is unlikely that all of these are references to Line of Duty.  The conclusion though is that this is not a rare spelling error and if this spelling is common then the similarity has little evidential weight.  If the spelling can be shown to be rare the evidence might then carry more weight. This weight of evidence can be best expressed as a ratio of the probabilities of the two hypotheses although studies show juries struggle to understand these Bayesian likelihood ratios when expressed mathematically.

It’s not enough however to only know population rate for the “definately” spelling.  A forensic linguist is above all a linguist and understands how language varies across communities.  Spellings which are globally rare can be locally common.  Research would be required to show the differing rates of occurrence of “definately” in the staff of the Central Police rather than in the general population. Spelling variants will also be more or less common across different genres of communication as lots of creative spellings are acceptable in online communications such as internet chat.  The most difficult and time-consuming part of providing a forensic authorship analysis is identifying and collecting the best comparison samples.  There are always compromised decisions in this respect.  Can I collect the language of police generally, or should I focus just on Central Police? Can I use the email database when the questioned messages are online chat? And so on. These are just some of the reasons why a lack of certainty can be a true mark of a forensic linguistic expertise. 

I would couch my report in terms of points of distinctiveness and consistency across the questioned samples, the known samples and the comparison corpus.  I would definately never use 95% certainty.  AC12’s forensic linguist however, appears to be uninterested in base rates, uninterested in the cross-genre nature of their analysis, and has expressed their result as a percentage certainty of match.  We have grounds to ask are they incompetent, or are they bent?

I am Professor of Forensic Linguistics and Director of the Aston Institute for Forensic Linguistics.

I am an academic practitioner and a practitioner academic in the field of forensic linguistics.

I am an experienced academic, skilled in teaching, productive in research and engaged in a range of administrative roles.  

I have attracted research income in excess of eight million pounds since I joined Aston University in 2007 and I led the development of the Centre for Forensic Linguistics (CFL) into the Aston Institute for Forensic Linguistics as the internationally leading research group in the discipline.  

I am also a practitioner academic – my casework has helped resolve numerous cases nationally and internationally.  These cases relate to the criminal law, issues of national security and civil matters:

• I have contributed evidence in many criminal trials, for prosecution and defence, in cases involving terrorism, murder and sexual assault.
• I have been involved cases where forensic linguistic evidence was critical in providing evidence for arrests where several hundred lives were at issue.
• I was involved in the Yukos arbitration hearings which upheld a $50bn award against Russian Federation.  

Work such as this has drawn media attention and I am at ease engaging with press, television and radio.