Singapore opens a coroner's inquiry into the death of US engineer Shane Todd, whose parents believe did not commit suicide.
Shane Todd's death, in June 2012, was registered as a suicide by hanging.
But his family allege foul play was involved, pointing to work they say was linked to China's Huawei Technologies.
Both Huawei and Mr Todd's employer, a Singapore government institute, reject the claims.
Authorities in Singapore have been working with the US Federal Bureau of Investigation on the case after US officials called for Mr Todd's parents' concerns to be investigated.
The inquiry - which will focus on determining the cause of death - is expected to last until the end of May, after which a verdict will be issued.
Mr Todd's parents, Rick and Mary, are in Singapore and will be testifying.
Shane Todd, 31, an electronic engineer, was found hanged at his home in Singapore on 24 June 2012.
It was in a Financial Times report in February that Mr Todd's parents raised concerns about the circumstances surrounding his death.
They told the newspaper that what they found at their son's home did not match details in a police report related to his apparent suicide. They also said they did not believe he was the author of a suicide note shown to them by police.Mary and Rick Todd told the FT that the scene at their son's apartment did not match police reports
Mr Todd had been employed at the Institute of Microelectronics (IME) in Singapore, a unit under the state-owned Agency for Science, Technology and Research.
He had feared a project he was working on harmed US national security, his parents told the FT.
They picked up an external hard drive at his home, which the FT said contained copies of their son's computer files from IME, including a planned project apparently involving Huawei - a Chinese telecommunications giant - and IME.
Huawei has been labelled a potential national security threat by a US Congressional committee over fears about its ties to China's government and military.
According to the FT, the files detail a project using gallium nitride (GaN), a semiconductor technology that has both commercial and potential military uses.
IME and Huawei said preliminary talks to collaborate on a project did not progress.