Fred Warmbier, Otto's father, during a news conference after his son returned to the US last week. Credit:AP But plans changed after the coroner's office decided at the family's urging not to conduct an autopsy, instead limiting its examination to an external analysis of Warmbier's remains and review of his records, Zornes said. There was no immediate word from the family about why relatives opted not to perform an autopsy, which may have shed more light on the cause of the neurological injuries Warmbier suffered in North Korea. Warmbier's death came just days after he was released by the North Korean government and returned to the United States suffering from extensive brain damage and in a coma, according to the US doctors who treated him. Warmbier, an Ohio native and student at the University of Virginia, was arrested in North Korea in January 2016 while visiting as a tourist. He was sentenced two months later to 15 years of hard labour for trying to steal an item bearing a propaganda slogan from his hotel in North Korea's capital, Pyongyang, the nation's state media said.

American student Otto Warmbier is escorted at the Supreme Court in Pyongyang, North Korea, in March 2016. Credit:AP North Korean officials said that during his detention for "hostile acts against the state," Warmbier had contracted botulism, was given a sleeping pill and never woke up. Last week after the was brought home to Ohio, doctors there said Warmbier had extensive loss of brain tissue and had suffered a severe neurological injury. Otto Warmbier cries while speaking to reporters in Pyongyang, North Korea, in February 2016. Credit:AP It's unclear whether an autopsy could provide answers.

Experts say postmortem examinations can be illuminating, but the amount of time that has passed since Warmbier fell into a coma may limit what pathologists would be able to find. Daniel Kanter, medical director of the Neuroscience Intensive Care Unit, centre, speaks neuro specialists after Otto Warmbier was released to the US. Credit:AP Werner Spitz, a forensic pathologist who has worked on numerous high-profile cause-of-death investigations, said he was not very hopeful that Warmbier's autopsy would be able to shed light on what happened to him, given how long his body has had to erase the evidence. "After a year of this fellow being unconscious, it is a futile effort," said Spitz, who worked as a medical examiner in Baltimore and Detroit and is now a professor of pathology at Wayne State University School of Medicine. "He essentially died a year ago. But being on life support maintaining him artificially there are a lot of things that will not show any longer." Bruises, cuts and other superficial markings on the skin would be among the first to fade, likely leaving behind no trace that they were ever there. Damage to bones or organs might show scars, but it would be almost impossible to tell how long ago they occurred. If Warmbier had been arrested or otherwise mishandled by North Korean security officials in such a way that it affected his ability to breathe, Spitz said, "it will not show at all".

One exam that could provide a hint of what happened would be a closer look at the brain. Warmbier's doctors could tell there had been some damage to parts of the comatose student's brain when he arrived in the US. "Certain areas of the brain are more susceptible to oxygen deprivation than others. When those areas are affected, that tells you a lot about what happened in the past," said Spitz, whose past cases included the deaths of former US president JFK and Nicole Brown Simpson.. "And since he was conscious and well when he went there, and shortly he became unconscious, that all adds up together not necessarily in their favour over there." Brian Peterson, president of the National Association of Medical Examiners, said that it was clear that Warmbier suffered brain damage at some point. "One pathway to brain damage would be anoxia - insufficient oxygen to the brain," Peterson told The Washington Post in an email. "This could be caused by intoxication (think drug overdose), physical means (smothering, strangulation, mechanical asphyxia, etc.), or many other ways. Bottom line - months later - there would be nothing particular to find at autopsy except for the damaged brain. Another pathway to brain damage would be direct physical trauma - an impact to the head, or an impact by the head against something."

Peterson also said that "potentially, there could be physical findings months later in this case - a healed fracture, or macroscopic/microscopic brain changes consistent with impact." But he warned that even if a complete autopsy with neuropathology was performed, the results may not be specific enough to provide real answers. "It all depends on what happened to Mr Warmbier," he said. "That is why to forensic pathologists, history is so crucial. We need history just as much as clinicians do. Seriously, to withhold history (or fabricate it) can make our work difficult to impossible, at least in terms of producing meaningful diagnoses." Loading The circumstances of Warmbier's detention and what medical treatment he received in North Korea remain unknown. Reuters, Washington Post