A coroner’s inquiry that opened in Singapore on Monday may offer a final chance of resolving whether an American electronics engineer committed suicide – or was killed to stop him talking to the US authorities about his work at a Singapore institute on a sensitive research project involving a high-profile Chinese telecommunications firm.

The body of Shane Todd was found on 24 June 2012 by his girlfriend in his apartment in Singapore, hanging from a strap attached to a door. A police autopsy said his death was caused by asphyxiation, but his parents believe he was murdered. They said suicide notes purportedly left by their son were faked and the initial police account of the scene bore little relation to what they found when they arrived at the apartment 48 hours after his death.

Mr Todd, who was 31 when he died, had joined the Singapore government-backed Institute for Micro Electronics (IME) 18 months earlier and for the final year of his life worked on an IME project to develop an amplifying device, using gallium nitride (GaN), a heat-resistant material with the potential to make superconductors with many possible uses in the civilian and military fields. Mr Todd had been trained in the US on proprietary equipment that produces GaN but is restricted for export because of its potential military applications.

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During an early stage, IME was talking about the project with the Chinese telecom company Huawei, which is deemed a security risk by the US, Australia and India. According to his parents and his girlfriend Shirley Sarmiento, a Filipino nurse working in Singapore, Mr Todd was showing increasing signs of stress and unhappiness with his job as the project progressed.

Testifying on Monday as the first of at least 36 witnesses, Ms Sarmiento told the court that Mr Todd had frequently told her how he felt uncomfortable at IME and complained about the “dishonest environment” in his workplace. He had also mentioned how he feared “heavy hands coming after him”, she said.

Mr Todd had a history of depression dating back to his days as a college student, but in letters to his parents he had emphasised that his problem in Singapore was not depression but work-related anxiety. In particular, his parents, Rick and Mary Todd, told the Financial Times earlier this year that their son suspected he might be involved in a project that might be illegal, or something that in could compromise US national security. For this reason, they believe, he may have been murdered.

There are other apparent inconsistencies, apart from suicide notes that do not appear to be in Mr Todd’s handwriting. One of them apologised for being a burden on the family – but his mother pointed out he had never been a burden, but rather had excelled at everything he did.

According to the parents, the original police report described an elaborate mechanism for the hanging, including bolts drilled into the marble wall of the bathroom, that secured a pulley. But the Todds said they saw no trace of drilled holes when they arrived at the apartment from their home in Montana.

What they did discover, they told the FT, was an external hard drive. When they had it analysed by an IT expert in the US it was found to contain copies of their son’s computer files from IME, including a planned project apparently involving Huawei.

Friends have said that in the days before he died Mr Todd seemed in a much better mood, having secured a good job back in the US.

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His parents said they found boxes of his effects and clothes laid out as if for packing, as well as the air ticket to the US on a table. The place, they said, “looked like a snapshot of a man in the middle of a move”.

The official version, however, is very different. The state counsel, Tai Wei Shyong, told the court police found no signs of foul play when they arrived on the scene and no evidence that anyone had tried to force their way into his apartment. In addition, Mr Tai said, Mr Todd’s computer showed he had visited several suicide-related websites in the days before he died and had made 19 searches about depression in the last two months of his life.

Meanwhile, IME and Huawei have minimised their collaboration on GaN research. K Shanmugam, Singapore’s Foreign Minister and law minister, has said Mr Todd was involved in “a small project” with Huawei that lasted nine months. IME and the Chinese company had also discussed a possible GaN project, he added, but could not agree terms. “Thus the project never materialised,” Mr Shanmugam said.

The inquest is expected to last a fortnight and some time after that a verdict will be handed down, which under Singapore law cannot be appealed. But the Todds have vowed to seek an investigation by the US Congress, no matter the outcome.

“We believe China and Singapore are illegally transferring technology,” Mary Todd said last week.

“If our son was murdered, the implications for Singapore and China are so extreme that they will go to any lengths to make it look like suicide.”