Hertfordshire solicitor Martin Smith believes stage hypnosis can have serious effects on its subjects. Roger Pearson reports.

The recent high-profile damages action brought against television hypnotist Paul McKenna will make the public re-assess whether they should allow themselves to be exposed to stage hypnosis.

If that is the case, then Hertfordshire-based Martin Smith of Martin Smith & Co, who acted for the plaintiff in the case, believes that some good has come from the action.

McKenna left the High Court with a clean slate after Mr Justice Toulson ruled that it was "highly improbable" that hypnosis by him had been responsible for schizophrenia which developed in one of his subjects, 30-year-old Christopher Gates. Gates' £200,000 damages claim was dismissed.

But the allegation made by Gates concerning the ill-effects of stage hypnosis was by no means a one-off. Smith's casebook contains a number of claimants who say they have suffered after being stage hypnotists' subjects.

Smith's involvement came about when he was approached by hypnotherapist Derek Crusell. Crusell treats a number of patients who claim to have suffered ill effects after stage hypnosis. Smith has since become an expert on the subject, looking into the claims of many of Crusell's patients.

Although the bulk of claims have failed for various reasons, one is still active and heading for the courts, while the possibility of an appeal over the decision in Gates is also under consideration.

Whatever the result of the case, Smith believes stage hypnosis is a worrying phenomenon and, while he does not want to be seen as heading a campaign against the medium, he is firmly opposed to it and believes it to be dangerous.

It is impossible, he says, to escape the fact that evidence of eminent experts in the case suggested that stage hypnosis presented a substantial risk to a small number of people taking part. "The case has highlighted the risks, and my message to anyone thinking of going to a hypnotism show is don't."

He adds: "You could be one of that small group. It is this group who make the best hypnotic subjects and so are more likely to be selected by the hypnotist. The chances are you'll end up with a bad headache. But you could get something much worse."

Apart from the warning bells sounded by the case as far as members of the public are concerned, Smith says the case raises an important point on funding. He believes the case would be unlikely to have been taken on without the backing of legal aid. "I very much doubt whether I would have done it myself," he says.

"We are talking about four years of hard preparation – in the end we had some 300 pages of medical and scientific papers alone, quite apart from substantial trial bundles and masses of video evidence – and commitments to expert witnesses who still have to be paid in the event of the case being lost. The risks are considerable to the solicitor who takes on a case of this nature on this basis.

"Very few firms would be prepared to take a gamble and that is very worryingS cases which may raise points of public importance could end up never reaching court."