A Roman Catholic priest accused of killing a nun 26 years ago in a hospital chapel shaped stab wounds into an inverted cross on her chest to humiliate her, a prosecutor said Wednesday in closing arguments at his murder trial.

The Rev. Gerald Robinson was so angry with Sister Margaret Ann Pahl that he also tried to anoint her with her own blood in a "bastardized" version of the last rites, prosecutor Dean Mandros told the jury.

The defense countered that DNA evidence doesn't link Robinson to the crime. The nun's underwear and fingernails had traces of DNA that was likely from a man but not from Robinson, said his lawyer, John Thebes.

"They (prosecutors) can't make their case beyond a reasonable doubt forensically, and they know it," he said.

Robinson, 68, is accused of killing Pahl while she was preparing the Mercy Hospital chapel for Easter services. She was choked, then stabbed 31 times.

Prosecutors have not disclosed a motive in the slaying, which occurred a day before Easter in 1980. But Mandros suggested that Robinson's relationship with the nun was strained. He said Pahl, 71, had been upset "to the point of tears" over the way Robinson conducted Good Friday services.

Mandros said Pahl was a dominating, strict figure and that Robinson had a reached a breaking point with her. "He had had enough. He had taken a lot, but he was not going to take anymore," Mandros said.

Robinson, the hospital's chaplain who presided at Sister Pahl's funeral, was a suspect early on because he was near the chapel at the time of the killing and lied to police about hearing someone else confess to the slaying. But he was not arrested until two years ago.

Investigators found a sword-shaped letter opener in his room at the hospital that prosecutors now say was the murder weapon.

Two medical examiners said blood stains on a chapel altar cloth could have come from the letter opener. A detective testified that the blade on the letter opener was a close match with holes in the altar cloth.

Thebes suggested that Pahl was killed by someone who entered the chapel, strangled her and stabbed her using a pair of scissors that she owned but were never found.

Robinson faces a mandatory life sentence if convicted.