VIENNA, Austria (AP) _ The trial of an aging doctor accused in the deaths of nine children in a Nazi-run clinic was suspended indefinitely Tuesday after he was found to be suffering from worsening dementia.

Tuesday's court session was the third attempt to prosecute Dr. Heinrich Gross, 84, on charges linked to the deaths of thousands of children killed by the Nazis because they were deemed physically, mentally or otherwise unfit for Adolf Hitler's vision of a perfect world.

The judge ordered the suspension about a half hour into the session, after a court-appointed psychiatrist testified that Gross' dementia had worsened since two examinations in 1998.

Judge Karlheinz Seewald ordered more tests over the next six months, leaving open the possibility the trial could resume. However, because dementia worsens with age, it appeared unlikely that Gross would ever be prosecuted.

``I very strongly doubt whether Dr. Gross will ever be deemed fit to stand trial,'' prosecutor Michael Klackl said.

Under Nazi rule, 75,000 people across Europe, including 5,000 children, were murdered for being mentally or physically handicapped. Children were killed by injection, medical experimentation or simply starved. The Nazis called them ``unworthy lives.''

Gross was put on trial twice before, but the case was thrown out in 1950 because of legal technicalities and again in the 1980s because the 30-year statute of limitations on manslaughter had expired.

Prosecutors filed a new set of charges, accusing him of complicity to murder in the cases of nine children who allegedly died as a result of abuse.

Gross pleaded innocent, and his lawyer, Nicolaus Lehner, said Gross was at the war front during the time the nine children were killed.

Lehner has called the trial a politically motivated ``scandal'' at a time when Austria's Nazi past is under intense scrutiny. Austria's new government includes a far-right party whose leader, Joerg Haider, has praised the Hitler era.

Prospective witnesses included a survivor of the clinic, Johann Gross, who is not related to the defendant.

Johann Gross recalled the defendant giving him injections as punishment for trying to escape the institution. ``I would crawl on my hands, dragging my legs behind me because they were devoid of sensation,'' Gross said. ``Or I would throw up, again and again.''

He said some infants were left on hospital balconies near his dormitory overnight in winter. ``I heard them whimpering _ and then I heard the parents got a letter saying their child had died of pneumonia,'' he said.

After the war, Heinrich Gross became a prominent neurologist, publishing research based on the preserved brains of children killed by the Nazis.