A judge has ordered Maine’s chief medical examiner to explain his change in opinion that derailed a murder trial last week.

Dr. Mark Flomenbaum arrived at the Cumberland County Courthouse on Tuesday to testify about an autopsy he performed three years ago. As he prepared to take the witness stand, Assistant Attorney General Meg Elam showed him a photograph of the wound that would be entered as evidence that morning. He then told her he needed to change his findings about the angle of the fatal shot, a key factor in the case – one that determined the shooter’s distance to the victim.

The pathologist’s reversal prompted a mistrial and baffled legal experts. It was an example of the faultiness of forensic evidence, and it is still not clear how significant the impact of the new opinion will be.

“Everything is in the photograph,” said Dr. Lawrence Koblinsky, a forensic scientist and a professor at the John Jay College of Criminal Justice in New York. “Where did it come from? Who took it? What does it mean?”

Noah Gaston

Alicia Gaston, 34, died from a single shot in the stairwell of her Windham home on Jan. 14, 2016. Her husband, Noah Gaston, has said he fired the shotgun because he believed she was an intruder. Police pointed to inconsistencies in his story from the start, and he was charged with murder and manslaughter. Gaston, now 36, has been held without bail at the Cumberland County Jail ever since his arrest.

Superior Court Justice Michaela Murphy urged the lawyers to bring the case back for a new trial as soon as possible, and she said she did not find evidence of misconduct on either side. The photograph in question has been sealed. State officials have declined to answer questions about the case, and a spokesman for the Maine Attorney General’s Office released its first public statement about the sudden development on Friday.

“The Court found that neither the Attorney General’s Office nor the Office of the Chief Medical Examiner did anything wrong in this matter and the State stands by the Court’s determination,” the statement said.

Flomenbaum has refused to comment on the case.

Defense attorney Robert Andrews said the judge gave Flomenbaum 30 days to explain his change in opinion.

“Until we know what his explanation is, it really isn’t appropriate for us to speculate as to the implications of those reasons,” Andrews said Friday. “We don’t know if he did this because he was pressured, and we don’t know if he did this because he’s incompetent, or we don’t know if he did this because it was a judgment call and he made the wrong one. All we know is we have a family of a victim that is suffering and a man who continues to stand accused of a very serious crime.”

FORENSIC EVIDENCE NOT INFALLIBLE

Gaston’s attorneys had chosen to rely on the state’s forensic evidence rather than challenge it. Andrews told the judge Thursday that the defense team had a ballistics expert review the evidence, and that person did not see any problem with the state’s findings. When Andrews argued his request for a mistrial in court Thursday, he said he considered that evidence “infallible,” but the judge immediately challenged him.

“I think one thing we’ve learned in criminal forensics is that very little forensic evidence is infallible,” Murphy said. “I think we’ve learned that over time in very profound ways on cases where convictions have not been valid. I’m not talking about anything like that here, but I think we should be careful using the word infallibility when you’re talking about evidence.”

Legal experts agreed forensic evidence is not foolproof, but they said this scenario is highly unusual.

Court documents show Flomenbaum conducted the autopsy on Alicia Gaston the day she died. Also present were a technician and three detectives from the Maine State Police. The medical examiner released a report within days of Alicia Gaston’s death that said the wound path was “very slightly downward.” Flomenbaum then placed a rod in a forensic dummy to simulate the wound path. That directional rod, along with lead residue and blood splatter, led investigators to determine that Alicia Gaston was at the top of the stairs when her husband shot her.

When he saw the wound photograph last week, Flomenbaum told the prosecutors that the path could have actually been as much as 45 degrees downward. That calculation could mean Alicia Gaston was lower on the staircase when she was shot.

APPROPRIATE RESPONSE: RESTART

Jim Burke, a clinical professor at the University of Maine School of Law, said a mistrial was the appropriate response to such a dramatic development.

“They’d already made their opening statements and predicated the entire trial on the medical opinion that this is the path of a shot, and the path substantially changed,” Burke said. “It can’t go forward. You have to draw a line and restart.”

Koblinsky, the forensic scientist, said shotguns create wounds that are harder to trace than other types of guns. He questioned why no other expert challenged the wound path until Flomenbaum changed his own testimony, and he said the defense team is likely to seek outside opinions for a new trial. Medical examiners can offer contradicting findings based on personal experience, he said.

“It is not science,” he said. “It is art.”

Gaston’s lawyers had hinted to the jury that he would testify in his own defense. Hermann Walz, a longtime trial attorney and an adjunct professor at John Jay College, one of the top criminal justice schools in the country, said the change in forensic evidence would probably not cause them to reverse that decision.

“A case like this really does boil down to the defendant,” he said. “The defendant almost has to testify in a case like this, get up and tell his story.”

Because Gaston immediately admitted to shooting his wife, a central question for the jury was whether he knew what he was doing that early winter morning. Both sides saw the forensic evidence as a way to answer that question.

In her opening statement, the prosecutor told the jury that forensic evidence would prove the couple was very close together when he fired the gun. Elam said Gaston recognized his wife and intended to kill her.

“This was a killing without justification,” she said. “This is a crime.”

Andrews said in an interview Friday that photos of the forensic dummy on the stairs show Gaston could not have seen his wife’s face.

“In our view, that was powerful evidence verifying what it was that Mr. Gaston said occurred,” Andrews said.

‘A COMPLETE MYSTERY TO EVERYONE’

The jury had only heard a fraction of the evidence at the end of the first day of testimony. For example, it remains unclear whether the defense will introduce the findings of a psychological exam meant to determine if Gaston was in an abnormal state of mind at the time of the shooting. It is not clear how dramatically the medical examiner’s report to the judge will impact the strategy for either side.

The defense team told the judge a different opinion from Flomenbaum at the outset would have changed their approach. They have contacted an outside expert who could review the new information and testify at a new trial.

But Elam told the court she still sees the shooting as a crime. She pointed to other forensic evidence, like the lead residue and the blood splatter, and she suggested the gun could have been at an angle when Gaston fired.

“No matter where she was on the stairs, it was still a murder,” Elam said. “Certainly we are not going to pretend that we don’t believe based on the forensic evidence that she was at the top of the stairs.”

Legal experts said the mistrial could prompt new plea negotiations, but neither side has commented on that possibility. A new jury would not be allowed to know the judge had already declared a mistrial in the case, but the trial could possibly include testimony about the state medical examiner’s change in opinion.

Andrews said a new trial could take place as soon as November, but their next steps depend on the answers from Flomenbaum.

“This is a complete mystery to everyone,” Andrews said. “Everyone here deserves an explanation.”