Story highlights Parents of American Shane Todd walk out of Singapore inquiry into engineer's death

Mother says an exhumation may be only way to prove family's contention he was murdered

The Todds contend their son was murdered because of his knowledge of research project

The companies IME and Huawei assert no project agreement was concluded

The parents of American Shane Todd, found hanging in his Singapore apartment last June, tell CNN they may exhume their son's body to conduct an autopsy in the United States.

Todd's mother Mary says an exhumation may be the only way to prove "for sure" the family's contention that he was murdered.

The Todds walked out of the Singapore inquiry into their son's death earlier this week, saying, "We've lost faith in the process" and Singapore's inquiry process was "pre-determined" to conclude their son's death was a suicide, and that police and investigators never considered evidence that may suggest Todd was murdered.

"We told the police at the very beginning. We talked to Shane every week for three months at least, all the way up to June when he passed away, (and he said) that he was in fear for his life," Todd's father Rick told CNN. "You would think they would look into it. But none of that happened."

The inquiry into the death of Todd, found hanging in his Singapore apartment on June 24, comes after Singapore's medical examiner concluded that Todd committed suicide. State attorneys said during the hearing that Todd's laptop shows he accessed suicide-related web pages in the months before his death, with a search in March on how to tie a hangman's noose. But Todd's parents -- who had flown from their home in Montana to attend the hearings -- claimed there was evidence that his death was a homicide.

The Todds claim their son was murdered because of sensitive knowledge he had of a project using gallium nitride (GaN) between the Institute of Microelectronics (IME) -- a Singapore government-backed research agency -- and the Chinese telecom giant Huawei.

GaN is material that can withstand high temperatures and can be used in power amplifiers with a range of applications from light emitting displays to radar communications.

Documents found on Todd's laptop after his death reportedly indicate IME may have had plans with Chinese telecom giant Huawei to co-develop an amplifier using GaN. Such a device could have both military as well as civilian uses. The 31-year-old Todd had been working for 18 months at IME when he decided to quit his job and return home to the United States shortly before his death.

Employees of IME have testified that there were several meetings held with Huawei, including a meeting with their senior level employees that Todd attended, but both IME and Huawei assert no project agreement was concluded, according to testimony.

Patrick Lo, deputy executive director of research at IME and Todd's supervisor, testified that his agency does not conduct any classified military research.

The Todds say they have evidence to show their son had been instructed to hand copy a GaN "recipe" or formula from a U.S. vendor where Todd had been sent for training.

The family says he had been left alone in a room to hand copy formulas, and say evidence from Shane's computer shows he had handwritten "highly sensitive recipes."

Lo denied in court that he had instructed Todd to hand copy recipes and said hand copied recipes would be inaccurate and therefore "useless."

The Todds stood up in the middle of the inquest proceedings Tuesday and walked out in objection to a witness they were unfamiliar with -- a friend and former work colleague of their son's who testified he'd had a beer with him the night before Todd was found hanging on June 24.

"We're getting sprung stuff at the last moment," Rick Todd said outside court. He said the state had given them no prior notice of the witness Frenchman Luis Alejandro Andro Montes.

The Todds said they had been "told from the beginning that this will be honest and open" and pointed out that their own lawyers had just hours before been chastised by Singapore's judge Chay Yuen Fatt for introducing last-minute documents.

Singapore Senior Counsel Tai Wei Shyong referenced Montes in his May 13 opening statement and at that same time said the state would try to bring Montes in as a witness.

Just hours before, a key witness for the Todd family, American medical examiner Dr Edward Adelstein, retracted his original assertion that Shane Todd had been strangled by a cord and hanged. Testifying via video link, Adelstein agreed with other forensic pathologists in the case including two U.S. medical examiners, who reviewed the case at Singapore's request, that there would need to be evidence of internal neck injuries if Todd had been "garroted."

However, Adelstein continued to assert that Todd had been murdered and speculated that he had been killed and then hanged to make it look like suicide.

"I have to assume that people who know how to kill you can do it in a way that is difficult to detect," Adelstein added.

He did not examine Todd's body and came to his initial conclusions on the basis of photographs taken by the family just before the funeral and Singapore's autopsy report.

His new opinions come after the family provided him with a series of photos obtained from Singapore police and forensic officials.

Questioned about the photos by a lawyer for the state, Adelstein admitted, "The cause of death is difficult for me to say."