In check

For months after his arrest, Ian Huntley denied having anything to do with the deaths of Holly Wells and Jessica Chapman. But when crucial mobile phone evidence placed Jessica's phone inside or just outside his house when it was turned off, Huntley finally admitted the girls had died inside his house. When Ian Tomlinson, the newspaper vendor struck down by police at the G20 protests in London in 2009, was first examined after his death the forensic pathologist concerned concluded that Mr Tomlinson's death was due to natural causes. That an officer is now facing manslaughter charges over his death illustrates how comprehensively that conclusion has been rejected. These two cases highlight the importance '“ and fallibility '“ of expert evidence incriminal cases.

Toxicologists carry out back calculations of the alcohol present in a driver's blood stream at the time they were stopped by police. Forensic computer experts analyse fragments of files and deleted content in a suspect's computer to find evidence of indecent images. Scenes of crime officers look for footprints (and, in one memorable case, ear-prints) at crime scenes and compare them with the wear and tread of the shoes worn by a suspect.

Fraud trials are often perceived to be complex, lengthy and costly, but such perceptions fail to take account of the huge amount of time that judges, prosecutors and defence lawyers devote before a case begins to ensure that only the relevant areas of dispute are challenged. This often involves early service of expert witness reports, and attempts in correspondence to limit any areas in dispute.

Such attempts are usually successful: the vast majority of criminal fraud cases involve little dispute on the facts, and correspondingly little unresolved dispute involving experts. The central, jury-decided, issue underlying most contested fraud cases is the defendant's state of mind at the time the offences were alleged. That is, whether he or she held the requisite dishonesty in committing the fraud.

If expert evidence does decide the outcome of a case, it is usually before the jury gets into court. In one memorable case some ten years ago, a woman had been accused by her estranged brother of forging his signature on the transfer forms in respect of their jointly owned house, and making off with the proceeds. With the help of expert handwriting evidence, the defence was able to prove that not only had he signed the transfer forms, he had probably forged a number of other documents he was now trying to use to build a case against his sister. The prosecution offered no evidence. Experts do still line up against one another in relation to 'fitness to plead' cases.

The test of fitness to plead was established in the case of Pritchard (1836). Essentially, the judge must be satisfied that the defendant 'is of sufficient intellect to comprehend the course of proceedings on the trial, so as to make a proper defence '“ to know that he might challenge [any jurors] to whom he may object '“ and to comprehend the details of the evidence'.

When the issue of fitness to plead is raised by the defence, they must establish it on the balance of probabilities. If raised by the prosecution, the burden is to prove the matter beyond reasonable doubt. If the judge finds that the defendant is unfit to plead, the jury will then be asked to consider whether, on the facts, the defendant actually committed the acts as charged.

As the Pritchard test requires an assessment of the defendant's ability to understand the evidence, the instructed expert must bear in mind the nature of the evidence when dealing with the client.

Often, evidence in fraud cases is complex and voluminous. For this reason, the defence expert must understand the stresses that may be placed on the client in defending lengthy fraud proceedings, and will take into account the additional burden fraud evidence may have on the client.

From a practical perspective, prudent defence lawyers will ensure that their cases will be prepared with the expert's needs in mind and will provide them with: a full proof of evidence, setting out their client's personal as well as career history (where relevant); observations of the client's behaviour in stressful environments, such as during police detention, questioning in interview and court appearances; and full details of the prosecution case including explanations of any complex areas such that the mental health expert is able to properly assess the client's ability to comprehend such information.

The dangers

However, while defence lawyers argue that their clients are unfit to plead, prosecutors may (and often do) view the situation differently. They may ask for the defendant to be independently examined to determine whether he is deliberately feigning unfitness to plead, i.e. malingering.

In R v Mohammed Sharif [2010] EWCA Crim 1709, Mr Sharif had been convicted in 1999 of conspiracy to defraud, for which he was given a three-year custodial sentence. The history was that, in 1985, when Mr Sharif was 15 years old, he sustained a head injury which resulted in severe deterioration of both his physical and mental condition. In 1986, Mr Sharif's father applied to the Criminal Injuries Compensation Board for compensation of his son's injuries. In 1996, the police conducted an investigation on suspicion that Mr Sharif and other members of his family were involved in a large-scale insurance fraud. This was because Mr Sharif's father had made a number of insurance claims involving his son and other members of his family.

As part of this investigation, the police seized a family video, which identified a man (purportedly Mr Sharif) behaving perfectly normally at a time when was he was supposedly severely brain damaged. Fitness to plead became a live issue. Professor Deakin examined Mr Sharif in 1994. His opinion was that the family video showed a clear case of 'malingering' and there was no psychiatric or neurological cause. This opinion was supported by another medical expert who said that Mr Sharif was fit to plead and that it was highly improbable that he was suffering from any serious mental illness or organic brain disorder.

In January 1999, Mr Sharif was found to be fit to plead (at that time, the issue of fitness to plead was left to the jury, but now this is a matter that is decided by the judge alone). The trial went ahead and Mr Sharif was eventually convicted.

In May 2001, an application was lodged with the Criminal Cases Review Commission, on the ground that there was fresh medical evidence to show that Mr Sharif had not been fit to stand trial.

A number of experts were consulted and the central opinion expressed was that Mr Sharif was actually suffering from an organic brain disease, and that the impairments were so severe, that it was unlikely that he had been faking his impairments.

He in fact suffered from a rare genetic condition which occurred as a result of consanguineous marriages in his family '“ a condition not identified until specialists in this field were consulted. Armed with this new information, Professor Deakin, the expert who initially gave evidence in court for the prosecution, reviewed his findings and came to the conclusion that Mr Sharif was not fit to plead.

While this case is unusual owing to Mr Sharif's rare medical condition, it shows that no expert is infallible, and reinforces the need to ensure that clients have access to the best medical experts available. Ultimately, the role of the defence lawyer is to gather as much information as possible to assist the expert, and, in Mr Sharif's case, this would have included taking a detailed family history. Had his genetic condition been diagnosed earlier, he may well have been given medical treatment rather than a prison sentence.

Even if a client is considered fit to plead, a medical, psychiatric or psychological report may be useful both during and after the trial. Conditions which affect concentration or general health (such as back pain from sitting in one position for too long) should be taken into account by a judge when managing a trial, by setting appropriate times for breaks and the like.

The approach of many judges is to ask the experts whether the imposition of suitable conditions on a trial would enable it to go ahead without making the defendant's condition worse and/or ensure the defendant understands and can cope with the proceedings. And, if he is con-victed, his personal circumstances, which include his mental and physical health, must be taken into account by the sentencing judge.

The existence of personality disorders, the onset of depression, or other mental characteristics which could explain (rather than justify) an offender's behaviour may also assist him when he comes to be sentenced '“ particularly if the nature of his condition is that he is unable to demonstrate insight into his offence, that quality so beloved of probation officers.