TOLEDO, Ohio — A letter opener a Catholic priest kept in his top desk drawer is an exact match for the weapon used to kill a nun 26 years ago, a forensic pathologist told jurors in the cleric's murder trial Tuesday.

The witness, an assistant county coroner, testified that when the body of the nun was exhumed by cold case detectives in 2004, she placed the tip of the blade in a small puncture wound in the victim's jawbone.

"It was a perfect fit," Dr. Diane Scala-Barnett said.

She said the comparison convinced her the letter opener, "or a weapon exactly like this," was responsible for the 31 stab wounds suffered by Sr. Margaret Ann Pahl on April 5, 1980.

Scala-Barnett was one of four witnesses to testify about the letter opener Tuesday. Linking the dagger-shaped blade to the crime is critical for prosecutors pursuing a murder charge against the Rev. Gerald Robinson, 68.

Story continues

There were no eyewitnesses or obvious motives, and despite police suspicions of the priest, the crime remained unsolved until two years ago, when prosecutors said new forensic techniques allowed them to connect the letter opener to the crime scene.

Robinson maintains his innocence and his defense is expected to rebut the new forensic evidence with its own experts. North Carolina forensic anthropologist Kathleen Reichs, the inspiration for the Fox program "Bones," is expected to attack the analysis of Scala-Barnett and an anthropologist, Julie Saul, who echoed her findings Tuesday.

Prosecutors called Terry Cousino, a detective with the Toledo police department's scientific investigation unit, to recount his reexamination of a bloody altar cloth at the crime scene as part of the reinvestigation in 2004. Cousino said found distinctive stains that were similar in size and shape to the 8-inch blade.

As the detective testified, prosecutors rolled the bloody linen out in front of the jury box and invited panelists to walk around it. The jurors, four of whom are Catholic, bent over the cloth, inspecting holes made by the weapon that killed her.

Robinson, a diminutive man with graying hair, looked on impassively from the defense table. He retired from the priesthood after his arrest, but still wears his Roman collar to court.

On a large display screen, Cousino pointed out long, pointed stains which he said tracked with the shape and curve of the letter opener. He noted that a stain "kinda shaped like an acorn" resembled the knob at the end of the blade and a linear pattern mimicked the ridges in the handle.

The detective sent the cloth and the blade to Paulette Sutton, a Memphis medical examiner and one of the country's leading authorities on blood stain analysis, for further testing. She is to testify later in the case for the prosecution.

Cousino also testified that the first nine stab wounds — the only ones made through the cloth — formed an inverted cross with "exact symmetry."

He said that the wounds were so even and defined that the assailant likely used an actual cross as a guide.

"Not only did it fit the form of a cross, the symmetry and the precision would suggest to me that something was used as a template to put down on the cloth and stab around," Cousino said.

The detective said he had attempted to find other letter openers like Robinson's. The letter opener was a souvenir from a now defunct wax museum in Washington, D.C. Cousino said it was a highly unusual blade because it had four sides and an unusual medallion that depicted the U.S. Capitol. He said he searched thousands of listings on eBay and other sites, but never found anything like the blade.

In addition to a forensic anthropologist who echoed Scala-Barnett's testimony about the wound to the jawbone, jurors heard from Edward Joshua Franks, a retired criminalist who examined the letter opener in 1980 shortly after it was seized from Robinson's drawer. He said he found no blood on the blade itself and found the letter opener strangely clean.

"It was sumptuously clean. It didn't have any fingerprints, any stains, no smear marks. It appeared as if it had been polished and that was interesting," Franks testified.

He said he removed the Capitol medallion from the opener's handle and found a small stain. A presumptive test for blood came back positive, he said.

Asked if he performed a DNA test, Franks chuckled.

"No DNA then," he said. "No e-mails either,"

On cross-examination, Franks agreed that the test was not conclusive and that his results may have been a false positive.

Testimony continues Wednesday morning. The trial is being shown live on Court TV Extra.