SINGAPORE (AP) — An American engineer who was found dead in his apartment in Singapore last year killed himself, a judge ruled Monday, rejecting suspicions by the man's parents that he was murdered because of research into sensitive technology.

The U.S. Embassy described the inquest into Shane Truman Todd's death as fair and comprehensive, weeks after Todd's parents walked out of the hearings, saying they had lost faith in the process.

The 31-year-old engineer's body was found by his girlfriend in June 2012. State counsel presented evidence of links to suicide websites on his laptop and suicide letters written to family members and loved ones.

Judge Chay Yuen Fatt said Monday he found no evidence of foul play, ruling that Todd "committed suicide by hanging himself."

Chay recorded the official cause of death as "asphyxia due to hanging" and voiced hopes that Todd's family and loved ones would be able to find closure.

Todd's parents have said they believe he may have been murdered over his research in the U.S. into material used to make heat-resistant semiconductors, a technology with both civilian and military applications.

Rick and Mary Todd left Singapore in May before the inquest ended. They said they believed the evidence of suicide was faked and that officials had not followed protocol in the investigation, including in how they accessed Todd's computers and examined the location of his death. Singaporean authorities have denied the claims.

Mary Todd told The Associated Press by telephone from her home state of Montana that "today's result means nothing to us because we expected it." Her husband said last week the family no longer trusts Singapore's legal system.

"It was apparent that the state was only interested in proving suicide and that was why we left," Rick Todd wrote in an email.

The U.S. Embassy in Singapore said in a statement that the inquiry had been "comprehensive, fair and transparent."

It said embassy officers had attended the entire hearing, and that Todd's family had been given the opportunity to participate in the hearing and was represented by experienced legal counsel. It expressed sympathy to Todd's family and friends for their loss.

Singapore's Foreign Minister K. Shanmugam said in May that the family should have formally testified during the inquest, adding their assertions could have been properly addressed that way. The inquest ruling cannot be appealed.

Todd's parents said documents he had backed up from his work computer included a draft of a project outline between Singapore's Institute of Microelectronics — Shane Todd's former employer — and Chinese telecom giant Huawei on the development of a device that utilized gallium nitride.

The heat-resistant material has civilian uses in products like LED screens and cellphone towers, and military applications possibly for radar and satellite systems.

Todd had been trained in the U.S. on proprietary equipment that produces the material but is restricted for export because of the potential military applications. Singapore's Institute of Microelectronics has said neither Todd nor the company was involved in any classified research, while Huawei has said it had no cooperation with the institute related to gallium nitride.