The Supreme Court said that it was not justifiable to protect expert witnesses from claims that they had failed in their professional duty. The removal of a similar privilege from barristers had not had a negative effect, judges ruled.
One legal expert has said that the decision is unlikely to stop most expert witnesses from providing testimony in trials.
"I don't see this decision having a significant impact on experts' willingness to act," said Richard Dickman of Pinsent Masons, the law firm behind OUT-LAW.COM. "Professionals who provide a service to clients face the risk of a claim if they are negligent and they can take out insurance against that risk. Expert witnesses are now in the same position,"
"The decision acts as a reminder that, although an expert witness needs to be independent and has a primary duty to the court, he also owes a duty to his client," said Dickman. "Like any professional who is being paid for his services, the expert should carry out those services with appropriate skill and care. Provided he does just that, he should have little to fear, even if the opinions he gives are detrimental to his client's case."
Motorcyclist Paul Wynne Jones was hit by a car driven by a drunk, uninsured, disqualified driver. He said that he suffered post traumatic stress disorder (PTSD) and depression as well as physical injuries.
As part of a law suit he filed for compensation, Wynne Jones arranged for an opinion to be produced on his condition by a clinical psychologist, Sue Kaney.
She said initially that he was suffering from PTSD but later signed a joint statement with a psychiatrist hired by the insurance company on the other side of the case that said that Wynne Jones did not suffer PTSD and had been deceptive in his reporting of his condition.
Wynne Jones's lawyers asked Kaney about the difference between the two reports and said she told them that the statement did not reflect what she had agreed in a phone call with the psychiatrist; that she did not think Wynne Jones had been deceptive; and that she had not seen the other psychiatrist's report when discussing it with him on the phone.
Wynne Jones's solicitors said that this joint report meant that they had to settle his case for less than they would otherwise have managed. Wynne Jones sued Kaney and the question of whether she can be sued over evidence provided for a court was heard by the Supreme Court.
Lord Phillips said that the immunity was designed to prevent claims multiplying around an initial case as losers in a case sued witnesses.
"The immunity has its origin in a reaction to an actual or perceived tendency on the part of disgruntled litigants, or defendants in criminal proceedings, to bring proceedings for libel or slander against those who had given evidence against them," he said. "Thus the immunity originally took the form of absolute privilege against a claim for defamation and it extended to all who took part in legal proceedings."
The Court heard that immunity was necessary so that experts felt free to give their honest opinion, even when it was not in the interests of the person who had paid them to be a witness. That honesty would open them up to suits without immunity, it was argued.
Lord Phillips said that any witness, whether paid as an expert or not, should be honest and has a duty to the court, and that this need not lead to suits.
"An expert will be well aware of his duty to the court and that if he frankly accepts that he has changed his view it will be apparent that he is performing that duty," said the ruling. "I do not see why he should be concerned that this will result in his being sued for breach of duty. It is paradoxical to postulate that in order to persuade an expert to perform the duty that he has undertaken to his client it is necessary to give him immunity from liability for breach of that duty."
When barristers were stripped of some immunities from prosecution the result was not that they were subjected to large numbers of law suits without merit, the Court said.
"It was always believed that it was necessary that barristers should be immune from suit in order to ensure that they were not inhibited from performing their duty to the court. Yet removal of their immunity has not in my experience resulted in any diminution of the advocate's readiness to perform that duty," said the ruling. "It would be quite wrong to perpetuate the immunity of expert witnesses out of mere conjecture that they will be reluctant to perform their duty to the court if they are not immune from suit for breach of duty."
Lord Phillips said that the removal of immunity was unlikely to result in a rash of claims against expert witnesses.
"The present case is unusual in that, on the agreed facts, the respondent has admitted to putting her signature to a joint report that did not express her views. There is nothing vexatious about the present claim," he said. "Where, however, a litigant is disaffected because a diligent expert has made concessions that have damaged his case, how is he to get a claim against that expert off the ground? It will not be viable without the support of another expert."
"Is the rare litigant who has the resources to fund such a claim going to throw money away on proceedings that he will be advised are without merit? The litigant without resources will be unlikely to succeed in persuading lawyers to act on a conditional fee basis. A litigant in person who seeks to bring such a claim without professional support will be unable to plead a coherent case and will be susceptible to a strike out application," said the ruling. "For these reasons I doubt whether removal of expert witness immunity will lead to a proliferation of vexatious claims."
"I consider that the immunity from suit for breach of duty that expert witnesses have enjoyed in relation to their participation in legal proceedings should be abolished," said Lord Phillips, who said that the immunity from defamation suits over what is said in court that all witnesses enjoy should be preserved.
His view was supported by four other judges. Two judges disagreed.