Witness Immunity is the privilege exorcised by a witness that protects them from any from of civil proceeding in respect to evidence given by them during legal proceedings. Additionally the immunity covers things said or done in the course of preparing evidence for such proceedings. The reasoning behind this is rooted in public policy; witnesses should not be deterred from giving evidence by fear of having to defend actions against them in relation to what they said in court. In order to shield honest witnesses the courts have decided to grant absolute immunity even when this results in a shield protecting a malicious and dishonest witness. Immunity isn't even lost when a witness deliberately and maliciously makes false statements but does not apply to the fabrication of evidence.

Though the basis of witness immunity is reasonable, it seem contrary to the interests of justice that this protection could be potentially exploited by an untruthful witness.

A recent ruling however made by the Supreme Court has opened the way for professional negligence lawyers to be able to sue expert witnesses for beach of duty, revoking immunity they had previously enjoyed.

The case involved was Paul Wynne Jones Vs Dr. Sue Kaney. This case concerned the application by Kaney for summary judgement, striking out a claim for negligence against her by the claimant. Kaney sought to rely on witness immunity.

Jones brought a claim for personal injuries following a road traffic accident. Dr Kaney had been instructed to prepare an expert psychology report on his behalf in that case. In her initial report, Dr Kaney suggested a diagnosis of post traumatic stress disorder. The defendant's expert took a different view (he believed that Mr Jones was exaggerating his physical symptoms). The experts discussed the case and prepared a joint statement. The statement was signed by both experts and was very damaging to Mr Jones' case, resulting in the claim settling for considerably smaller sum than originally claimed. It transpired that Dr Kaney had signed the joint statement prepared by the defendant's expert, thereby agreeing with its contents, without any comment or changes. The claimant subsequently issued proceedings for negligence against her.

In her application for the summary judgment to strike out Jones' clain, Dr. Kaney sought to rely on the court of appeal decision in Stanton v Callaghan (2000).

The High Court Judge found in Dr Kaney's favour, considering himself bound by the decision in Stanton v Callaghan. However, the Judge stated that "although I conclude that [Stanton v Callaghan] remains good law, I have doubts as to whether it will continue to remain so for the reasons canvassed by the Claimant and the discussion summarised above. I conclude that there is a substantial likelihood that on re-examination by a superior court, with the power to do so, it will emerge that the public policy justification for the rule cannot support it". The Judge therefore granted Mr Jones a certificate under section 12 of the Administration of Justice Act 1969 enabling him to apply to the Supreme Court for permission to appeal, without the need for the appeal to be heard first by the Court of Appeal.

The witness immunity rule has traditionally been justified by reference to the public interest in expert witnesses giving truthful and fair evidence in Court, without fear of being sued by a party whose case is lost. The clear message from the Court is that it is likely the immunity for experts will either be gotten rid of or just ignored in the future.

Although the Court currently has the power to sanction irresponsible experts by restricting their recoverable costs or, in extreme cases, disregarding their evidence altogether, it is ultimately the instructing party that is most affected by all of these measures. A change in law so that expert witnesses are more accountable to their instructing parties is arguably likely to increase the standard of expert evidence. Expert witness work provides a great source of income (especially in the current economic climate); however, as it stands, any professional can present themselves to the court as an expert, knowing that mistakes can be made without any serious consequences. However, the principle of independence must also be safeguarded.

Also, expert witnesses already have the safeguard, as with all other professionals, that they will not be held liable for negligent advice unless it is unreasonable (the advice must be such that no reasonable professional, competent in the field and acting reasonably, could give). It seems very unfair that experts have immunity from civil suits as well.