PORTLAND — Expert witnesses who testified Thursday in Dennis Dechaine’s hearing on a new trial offered contrasting views on whether the DNA evidence at issue is a result of contamination.

Three DNA experts, with doctorates in genetics and extensive backgrounds in forensic science, testified about the partial DNA profile that is at the center of the multi-day hearing. Dechaine’s lawyer, Steve Peterson, is trying to convince a judge that the jurors would not have convicted Dechaine of the 1988 murder and kidnapping of 12-year-old Sarah Cherry had they known about the DNA from an unknown male on the girl’s left thumbnail.

Two witnesses for the state testified that the autopsy conditions described to them posed a high risk for DNA contamination. At the time, DNA technology was new and lacked the kinds of safeguards that are used today.

In 1988, the State Medical Examiner’s Office did autopsies in the morgue of the Kennebec Valley Medical Center in Augusta. Earlier testimony indicated that instruments were kept in a metal tool box with towel-lined drawers. Instruments were sometimes rinsed and sometimes simply put back into the drawers. The towels got soiled with blood over time and were changed after several months.

“That scenario that you described would really be a textbook recipe for the potential for contamination for many, many steps along the way,” Frederick Bieber said after the conditions were recounted by Deputy Attorney General William Stokes.

Bieber, who holds positions at Harvard Medical School and Brigham and Women’s Hospital, said he has been at autopsies done under similar conditions, and dozens of people would handle instruments.

It probably wasn’t until the early 1990s that precautions to prevent DNA cross-contamination became widespread in autopsy rooms, he said. Before then, it was common for autopsies to be done with bare hands. The first precautions were not related to DNA, but to guard against the transmission of infections like HIV or to protect cells that would be cultured.

Carll Ladd, supervisor of the DNA section of Connecticut’s forensic lab, agreed that the conditions at the time of Sarah Cherry’s autopsy would have been “ideal” for contamination.

Another problem is that the hospital morgue probably was not a restricted space, so a number of people could be in the room and in proximity to the evidence, said Ladd, who also testified for the state.

He said airborne, or aerosol, contamination poses a great risk. That risk is addressed today with the use of facial masks and heating, ventilation and air conditioning systems.

A geneticist testifying for the defense said he does not believe the male DNA on the nail clipping got there through rampant contamination. Although there was a possibility of contamination, the lack of male DNA on other evidence suggests that is not the case, said Greg Hampikian, a professor of biology and criminal justice at Boise State University.

Particularly noteworthy is the clipping from the right thumbnail, he said, because it would have been taken at the same time as the left thumbnail, by the same person using the same instrument under the same conditions. The right thumbnail clipping had only Cherry’s DNA, while male DNA is on the left clipping.

That indicates the male DNA didn’t get on the left nail from dirty clippers, chemicals used in the testing or DNA floating in the air, said Hampikian, who is also director of the Idaho Innocence Project.

“It really bolsters the idea that there’s no contamination,” he said after the hearing concluded for the day.

No more testimony is scheduled for this week. The parties may reconvene after a couple of months, after the results of additional DNA testing on certain evidence become available.

Debbie Crosman, Cherry’s mother, said Dechaine’s ongoing appeals — four unsuccessful ones — have been difficult. She said she gets angry, cannot concentrate and has problems sleeping.

But Crosman said she needs to be present for her daughter, a smart girl who was mature for her age and already thinking about college when she was 12. Crosman imagines that, had she lived, she might have gone into teaching and would likely be married now and have children of her own.

“I’ve got to represent Sarah,” she said outside the courthouse.

Cherry was abducted from a baby-sitting job on July 6, 1988. A search for her and Dechaine, then a 30-year-old farmer in Bowdoinham, began after a notebook and a truck repair bill bearing his name were found in the driveway of the home.

Dechaine was seen walking out of the woods about three miles away that day. His pickup truck was found nearby that night. The girl’s body was found two days later, about 450 feet from where Dechaine’s truck had been. The rope binding her hands and the scarf around her mouth and neck were from the truck.

Dechaine said he went into the woods to inject speed and was alone and lost. He maintains that someone took the items from his truck.