Three Palestinian doctors found that Omar Asaad, 78, who had US citizenship, suffered from underlying health conditions.
They also found bruises on his head, redness on the wrists from being bound and bleeding in his eyelids caused by being tightly blindfolded.
The report, a copy of which was obtained by The Associated Press on Thursday, concluded that the cause of death was a “sudden cessation of the heart muscle caused by psychological tension due to the external violence he was exposed to.”
Asaad was returning home from a social gathering on January 12, at about 3am, when Israeli soldiers who had set up a flying checkpoint in his home village of Jiljiliya detained him. Such random arrests are a common occurrence in the West Bank, which has been under Israeli military rule since Israel captured the territory in the 1967 Mideast war.
Palestinian witnesses said Asaad was roughed up before being bound and blindfolded, and then taken to an abandoned apartment complex nearby. Other Palestinians who were detained in the same building later that night said they did not realise he was there until after the soldiers left, when they found him unconscious, lying face down on the ground. They called an ambulance.
The Israeli military has said he was detained after resisting an inspection and later released, implying he was alive. It is unclear when exactly he died. Initial reports said he was 80 years old.
The unit that detained Asaad, Netzah Yehuda, or “Judea Forever”, is a special section for ultra-Orthodox Jewish soldiers. It was formed with the aim of integrating a segment of the population that does not normally do military service. But Israeli media have reported problems in the outfit stemming from the hardline ideology of many of its soldiers.
Israeli military spokesman Lt Col Amnon Shefler said the incident remains under investigation and that “actions will be taken if wrongdoing is found”.
The State Department has said it is in touch with the Israeli government to seek “clarification” about the incident and that it supports a “thorough investigation”. US officials did not immediately respond to a request for comment on the autopsy.
The Israeli human rights group B’Tselem said Asaad’s detention was “bizarre.”
“This is a very small, quiet village,” said Dror Sadot, a spokeswoman for the group. “There was no reason at all to take an 80-year-old and to drag him and handcuff him. I have no idea why they did it.”
Israel says it thoroughly investigates incidents in which Palestinians are killed by Israeli troops. But rights groups say those investigations rarely lead to indictments or convictions, and that in many cases the army does not interview key witnesses or retrieve evidence.
Ms Sadot said the fact that the military is still investigating more than two weeks after the incident, even with the added pressure of American scrutiny, indicates that any eventual conclusion will be another “whitewash”.
“I don’t know, but from our experience, it will lead to nothing,” she said.