VIENNA -- Celebrated jailhouse poet Jack Unterweger hanged himself on Wednesday, six hours after being convicted of the murders of nine prostitutes in Austria's most sensational criminal trial for decades.


The suicide of the former "model prisoner" and author, said to have killed women he had been commissioned to interview after he was paroled from an earlier murder sentence, left the case under a cloud of doubt that may never be dispelled.


Shocked by Unterweger's death and angered by what he termed a "faulty" verdict, his attorney Georg Zanger attacked State Prosecutor Karl Gasser, saying it would be "the biggest scandal of the republic" if justice was shown to have been miscarried.


Tape cassettes were found in the death cell of Unterweger, who was to have been sent to a penitentiary for dangerous and psychologically disturbed convicts. Their contents remained secret.


In 1976, the young man from a broken home in a seedy environment was sentenced to life for killing a German woman friend who lived next door.


A model prisoner, turning out critically acclaimed childrens' stories, a collection of poems, and a sensitive novel, he drew the attention of Austrian intellectuals who championed his cause. He was paroled in 1990 and feted on television talk shows.


He went on to write successful screenplays and was held up as an example of the power of rehabilitation.


Then he was commissioned to write about the seamy side of life in red-light districts around the world, and as he launched into his research, asking prostitutes about their fear of being slain, his own story began to darken.


The 11 murders of which he was accused were committed in Austria, Czechoslovakia and the United States in what the prosecution alleged was a nine-month killing spree from September 1990 to July 1991.


The evidence against Unterweger, while enough to convince his jury, was almost entirely circumstantial.


Detectives said they found the hair of one victim in his car, but Unterweger said it was odd that they could not also find one single dog hair, because his German shepherd Joy was his constant companion.


Forensic experts and criminologists from the FBI flew in to testify during the two-month trial in Graz, southern Austria, where the writer-convict hanged himself with a strip of clothing in the early hours of Wednesday.


Prosecutors and expert witnesses delved into the psychological makeup of the accused. A psychiatrist testified that he suffered from "narcissistic-sadistic personality disorder."


Unterweger struggled to keep his composure on Tuesday as the seven-man, one-woman jury pronounced him guilty by a majority verdict on nine of the 11 murder charges.


A small man with well-kept hair, he stood up to hear the verdict wearing his customary jaunty silk tie and well-cut suit. When it was pronounced, his eyes reddened and his lips compressed and he began to cry.