German prosecutors have shelved their Nazi war crimes investigation of a retired Minnesota carpenter whom the Associated Press exposed as a former commander in an SS-led unit, saying Friday that the 96-year-old is not fit for trial.

Munich prosecutor Peter Preuss told the AP that Michael Karkoc’s attorney had refused to allow him to be examined by a medical expert from Germany, and that his office’s decision was based on “comprehensive medical documentation” from doctors at the geriatric hospital in the US where he is being treated.

He said doctors there had provided prosecutors with a comprehensive assessment of Karkoc’s health over the past year, which was evaluated by a medical expert in Germany.

“There are no doubts about the authenticity of the documentation of his treatment,” said Preuss, who declined to provide specifics about Karkoc’s health on privacy grounds.

The German investigation began after AP published a story in 2013 establishing that Karkoc commanded a unit in the SS-led Ukrainian Self Defense Legion accused of burning villages filled with women and children, then lied to American immigration officials to get into the US a few years after the second world war.

A second report uncovered evidence that Karkoc himself ordered his men in 1944 to attack a Polish village in which dozens of civilians were killed, contradicting statements from his family that he was never at the scene.

Karkoc’s family, who live in Minneapolis, have denied he was involved in any war crimes.

Karkoc’s son and family spokesman, Andriy Karkos, said by phone Friday that he planned a statement later in the day about the case and that he looked forward to clearing his father’s name, but declined further comment.

The US Department of Justice has refused to say whether it has ever investigated Karkoc, citing its policy of neither confirming nor denying investigations.

Department of Justice spokesman Peter Carr said Friday he also could not comment on whether his office would now pursue deportation proceedings against Karkoc.

“As we have said previously, we are aware of the allegations but will decline further comment at this time,” he said in an email.

Efraim Zuroff, the head Nazi hunter for the Simon Wiesenthal Center, criticized the department for not having initiating deportation proceedings against Karkoc over failing to disclose to American authorities his role in the Ukrainian Self Defense Legion when he entered the US in 1949.

“They should have been aware of his presence in the United States a long time ago, and if they were aware and did not take any action, that’s very unfortunate, and I would say atypical, but it’s obviously a failure,” he said by telephone from Lithuania.

“If they weren’t aware of him then it means he slipped through the cracks, but once AP exposed him they should have moved ahead as quickly as possible.”

Poland also initiated an investigation into Karkoc, which remains open.

State National Remembrance Institute spokesman Andrzej Arseniuk told the AP on Friday that his office’s prosecutors are currently awaiting a reply from the US to a request for help identifying handwriting believed to be Karkoc’s.

The German investigation has taken longer than usual, because prosecutors first had to wait for a court ruling that they had jurisdiction in the case.

That came last year, when the Federal Court of Justice said Karkoc’s service in the SS-led unit made him the “holder of a German office”.

That gave Germany the legal right to prosecute him even though he is not German, his alleged crimes were against non-Germans and they were not committed on German soil.

Someone in that role “served the purposes of the Nazi state’s world view”, the court said.

When cases in Germany are shelved they can be reopened at any time if circumstances change, but in this case Preuss said that is very unlikely.

The news came on the day a Jewish newspaper in Britain reported that Stephen Ankier, a retired clinical pharmacologist whose Nazi war crimes research done in his free time helped lead the AP to Karkoc, had located a former rifleman in Karkoc’s unit living near Manchester.

Ankier said he hadn’t found anything linking the 90-year-old man to war crimes but passed details on to German, American and Polish prosecutors many months ago in case they wanted him as a possible witness in the Karkoc case.

Preuss would not say whether German investigators had planned to question him, but said the man is not considered a suspect.