THE majority verdict of guilty of murder in the O'Donnell case seems certain to provoke controversy. Many people will, no doubt, puzzled as to how a defendant labelled as "psychotic" by several witnesses can be held fully for his actions and sentence accordingly to life imprisonment.

In the end, the case turned on the issue of legal insanity. And insanity goes to the heart of the issue of criminal responsibility, it is important first to set out the legal significance of the term.

Insanity may be raised as a defence to a criminal charge or as a preliminary issue of fitness to plead. When raised as a preliminary issue, the question is whether the accused is capable of following the proceedings and instructing counsel. The issue is one of cognition and comprehension and is decided by a jury rather than one of medicine or psychiatry to be determined by experts.

Readers will recall that Mr Justice Lavan adjourned the O'Donnell trial in its early stages in order to have this question determined by a special jury.

The justification for a preliminary hearing of the issue of insanity is that, since an accused person is a party to the proceedings against him, he must be capable of playing a rational part in them. If he is found to be unfit to plead, the trial cannot continue until fitness is regained.

When insanity is raised as a defence to a criminal charge, the question is whether the accused was sane at the time he committed the acts that form the basis of the charge against him.

Broadly speaking, the issue is whether the accused knew what he was doing and could control his actions. Expert evidence that an accused was suffering from a serious mental illness usually one of the psychoses at the time of the incident is usually tendered in support of the defence.

But it is important to remember that psychiatric evidence is relevant only to the extent that it sheds light on the fundamental issue of criminal responsibility. Even if it is clear that the defendant was psychotic at the relevant time, he is entitled to an acquittal on the grounds of insanity if and only if the evidence discloses that his illness probably prevented him from understanding or controlling his actions.

This aspect of the insanity defence can be confusing to non lawyers, who often assume that the legal and medical conceptions of insanity are co-extensive. The importance of the legal conception was properly emphasised by counsel for both sides in the O'Donnell case.

Although the State did not concede that O'Donnell was psychotic when he killed his victims the burden of its case was that there was abundant evidence, including the fact that he sought to cover his tracks by destroying vital evidence and that the defendant knew what he was doing and could control his actions at the relevant time, not withstanding any illness or disorder from which he may have been suffering.

Although juries are not required to give reasons for their decisions, the majority in this case was obviously persuaded beyond reasonable doubt by this argument.

Similarly, defence counsel went to great lengths to direct the jury's attention beyond the medical evidence to the accused man's life history, albeit in an effort to show that the evidence as a whole disclosed a radical want of reason, such that the defendant was not criminally responsible for his actions.

The form of the insanity verdict "guilty but insane" which some were arguing for in this case has been widely criticised. It is said to be illogical, since the concept of criminal guilt entails responsibility, whereas the notion of legal insanity precludes it.

But this contradiction is more apparent than real. As Mr Patrick MacEntee SC pointed out in his closing address in the O'Donnell ease, the relevant legislation merely says that the accused is guilty of the act charged against him and not in the fuller sense normally associated with a criminal conviction.

Although English law now renders the verdict as "not guilty by reason of insanity", there is much to be said in favour of the Irish formula. Given that the insanity verdict leads to automatic indeterminate detention in the Central Mental Hospital and that the normal consequence of an acquittal is the unconditional liberation of the accused, the Irish formula is arguably less misleading than its English counterpart.

The effect of the verdict automatic indeterminate detention in a criminal asylum has also been criticised. It is arguable that the courts should have the discretion conditionally or unconditionally to release a defendant who is no longer mentally ill when the verdict is delivered.

Such discretion would need to be sparingly used, but would be clearly appropriate in cases, like Ellis [1990], where the defendant secured the benefit of the insanity defence on account of the psychological effects of a physical illness that had been successfully brought under control by the time he came to trial.

It used to be possible for persons detained in the Central Mental Hospital as a result of the insanity defence to apply to the courts for release on the grounds that they were no longer insane and therefore no longer a danger both themselves and others.

This course of action was closed off by the Supreme Court in Gallagher [1991]. There, the court held that since a verdict of guilty but insane is an acquittal, the question of whether and when a detainee should be released from hospital is exclusively a matter for the Government.

(The contrary argument is that as the verdict was a kind of conviction, detention pursuant to it was a sort of sentence and that sentencing was a matter for the courts under the Constitution).

The difficulty with this arrangement is that it is no longer clear that the decision continue person's detention in the Central Mental Hospital is tied to the questions of mental illness. Indeed the Gallagher saga suggests that it is not, notwithstanding that the guidelines given to ministerial committees clearly indicate that it should be.

Gallagher shot and killed his former girlfriend and her mother in front of witnesses in the grounds of Sligo General Hospital. He was acquitted of murder on the grounds of insanity by a 10-2 majority verdict and automatically detained in the Central Mental Hospital.

Since then several special committees appointed by the Minister for Justice have declined to recommend his release, notwithstanding the fact that Gallagher has been protesting his sanity since shortly after his detention began.

THE Gallagher saga also highlights the danger that the Central Mental Hospital could become a form of punitive detention for defendants who, with the benefit of hindsight, the Government may feel should have been convicted of manslaughter or even murder rather than acquitted on the grounds of insanity.

As I argued here previously, the obvious solution to this problem is to establish a statutory review body to monitor the progress and, where appropriate, recommend the release of patients detained in the Central Mental Hospital, whether as a result of an acquittal on the grounds of insanity or of a finding of unfitness to plead.

In recent years the medical authorities in Dundrum have endeavoured to ensure that patients at the hospital are not detained longer than is necessary for therapeutic purposes.

The establishment of an independent review body to which the hospital authorities would be obliged to report at regular intervals, and to which patients would have a right of appeal, would help to ensure that past mistakes are not repeated and effectively put an end to the system where the Government is free to ignore recommendations for release coming from the Central Mental Hospital.

An unfortunate feature of the O'Donnell case was that the jury did not have the option of bringing in a verdict of diminished responsibility. This plea is designed to cater for defendants who are not insane but who, by reason of mental illness or abnormality, are not fully responsible for their actions. It allows for conviction for manslaughter and enables the court to impose a custodial sentence and/or make a treatment order.

It also has the advantage of comprehending disorders such as personality disorder (from which it was common cause O'Donnell was suffering) and psychopathy that do not typically affect a person's ability to understand or control his actions in the way that the psychoses and schizophrenias usually do.

As its name suggests, it is ideally suited to defendants like O'Donnell who seem to be stranded between the realms of full responsibility and legal insanity. The defence of diminished responsibility has been available in England since 1957. Rumours of its arrival on the statute book here have been around for some time, but regrettably these have so far proved to be exaggerated.