A Singapore coroner ruled Monday that a US scientist found hanged in the city-state in 2012 committed suicide during a bout of depression and was not murdered as his family claimed.
The US government, which had expressed strong interest in the case of electronics engineer Shane Todd, said the coroner's inquiry was "comprehensive, fair and transparent".
The body of 31-year-old Todd was discovered by his girlfriend in his flat in June 2012, sparking a controversy that reached the highest levels of both governments after his parents refused to accept Singapore police findings that he killed himself.
The family, citing documents found in Todd's computer files, insists he was working on a secret project with military applications and murdered as part of a conspiracy involving a Chinese technology firm and a state-linked Singapore research institute.
There was no immediate reaction from the family to the ruling, which cannot be appealed.
"The evidence before me instead compels me to find, beyond reasonable doubt, that the deceased had committed suicide by hanging himself," state coroner Chay Yuen Fatt said in a written verdict.
The investigation was limited by law to the cause of death and the verdict did not address the family's conspiracy claims.
Chay told a packed court that evidence presented during a two-week public inquest in May was "inconsistent with the possibility that there was foul play".
He said the evidence also showed that before his death, Todd had suffered a relapse of depression.
Witnesses earlier testified that Todd had suffered from the condition as a university student and repeatedly surfed suicide websites shortly before his death.
"His psychiatric condition included suicidal ideations of an overall increasing severity over the last few months of his life, which he had masked from the people around him," the coroner said.
Todd's parents said he was murdered as part of a conspiracy involving his former employer, Singapore's Institute of Microelectronics (IME), and Chinese technology giant Huawei Technologies, a firm accused by US officials of involvement in espionage.
IME and Huawei said they only held preliminary talks on a potential project with commercial applications, but did not proceed.
The family attended the Singapore inquest in May but angrily walked out before hearings ended, saying they had "lost faith" in the proceedings.
During the hearings, their star witness, US pathologist Edward Adelstein, recanted an earlier theory that Todd was garroted with a cord in his own apartment.
Instead he presented a new scenario -- that Todd was killed by assassins who made his death look like suicide -- but offered no evidence.
In his verdict on Monday, coroner Chay rejected Adelstein's testimony, calling it "nothing short of bizarre and extremely unhelpful in the way that it detracted from the critical pathological issues before the court".
He said he did not doubt the "independence or competence" of two other US pathologists who affirmed the suicide findings.
Hours after the verdict was issued, the US embassy in Singapore said Todd's family "was given the opportunity to participate in the hearing and was represented by experienced Singapore legal counsel".
"The inquiry into Dr Todd's death was comprehensive, fair, and transparent," it said in a statement.
The lead Singapore lawyer of the Todds, Gloria James-Civetta, told reporters the family would issue a statement on a website they had set up called "Justice 4 Shane Todd".
The death was first thrust into the spotlight after the London-based Financial Times reported in February that Todd's family suspected he was murdered because of his work on a joint IME-Huawei project involving gallium nitride, a semiconductor material with military and commercial applications.
Singapore, which has close military ties with Washington, quickly moved to dispel allegations that it had improper ties with Huawei, sharing evidence with the US Federal Bureau of Investigation and expressing readiness to allow a US audit of the IME.
Singapore Foreign Minister K. Shanmugam told journalists after the verdict was issued that he did not expect US-Singapore relations to be affected by the Todd case and urged the family to accept the findings.
"Many of us are parents, we can understand the family's grief. At the same time we need the strength to face the truth, and not to make fictional and untrue statements and allegations," he said.