A series of court rulings has presented convicted murderer Charles Singleton, his lawyers and prison doctors with an agonising choice.

Should he take the medication voluntarily and be condemned to death or refuse them and be condemned to a life of psychosis? Under the US constitution it is illegal to execute an insane person.

In an extraordinary and sharply divided judgment, the court of appeals in St. Louis has ruled that Singleton should be forced to take medication which will make him fit for execution.

Following Monday's decision Singleton has decided to carry on taking the medicine until an execution date is set, after which he will stop taking it in the hope of influencing further appeals.

One dissenting judge described the ruling as "the barbarity of exacting mindless vengeance".

Singleton, who stabbed a shopworker to death in 1979, believes his prison cell is possessed by demons, that a prison doctor implanted a device in his ear and that he is both God and the supreme court.

In October 2001 an appeal court ruled that executing him would amount to cruel and unusual punishment because he is insane, and granted a stay of execution, sentencing him instead to life in prison without parole. In his judgment on Monday, Judge Roger Wollman said the courts did not need to consider the ultimate result of medicating the prisoner, arguing that its primary interest was having a sane inmate, and that execution was merely an unfortunate bypdroduct of that.

"Eligibility for execution is the only unwanted consequence of the medication," he wrote.

In a strongly worded dissenting statement Judge Gerald Heaney countered: "Singleton is not cured; his insanity is merely muted, at times, by the powerful drugs he is forced to take.

"This leaves those doctors who are treating psychotic, condemned prisoners in an untenable position: treating the prisoner may provide short-term relief but ultimately result in his execution, whereas leaving him untreated will condemn him to a world such as Singleton's filled with disturbing delusions and hallucinations."

Singleton was diagnosed as a paranoid schizophrenic in 1983 and has been on and off medication since then.

In October 2001 the appeals court ruled that it was not sure he would understand his punishment even when he is on medication. A few months later Singleton wrote informing them that his victim, who identified him shortly before she died, was alive and "somewhere on earth waiting for me - her groom."

Singleton's lawyer, Jeffrey Rosenzweig, is considering taking the matter to the supreme court.

Kelly Kristine of the Arkansas attorney general's office said the ruling was limited and correct. "The ethical decisions involving doctors are difficult ones but they are not ones for the courts," she said.