Colleagues of a US scientist found hanged in Singapore last year told a coroner's inquiry Friday he was not involved in projects with military applications and was never asked to compromise any country's national security.

High-tech researcher Shane Todd, whose death under disputed circumstances last June sparked global media attention, was part of a research team working on gallium-nitride (GaN), a semiconductor that can be used in radar and satellite communications.

Todd's parents allege their son was murdered after he had grown anxious the project he was working on for the Institute of Microelectronics (IME) was linked to a Chinese telecoms firm and could endanger US national security.

Medical experts have said that an autopsy report point to a suicide, but the family, backed by senior US officials, asked for a deeper probe.

"During his time at the IME, Shane was never asked to do anything that would compromise the national security of any country," Patrick Lo, deputy executive director for research at the institute, told the inquest on its fifth day.

"Shane was also never asked to obtain restricted or classified information and to provide them to other countries," said Lo, who was Todd's immediate superior.

The coroner's inquiry, which is due to last until May 28, will determine the cause of his death.

At the time of his death at age 31, Todd had just finished a stint with the IME, where he was part of a team working on GaN.

His former colleagues however told the inquiry there was nothing sinister about the project and that research on GaN is commonplace in the industry.

The London-based Financial Times reported in February that the scientist was working on an advanced amplifier using GaN which could have military applications.

The report said a computer hard drive discovered by Todd's parents at his flat after his death linked the amplifier project to Huawei Technologies, a Chinese telecom giant suspected by Washington of involvement in espionage.

But Lo at the inquiry reiterated IME's earlier assertions that talks between the institute Huawei on the development of a GaN amplifying device never progressed beyond preliminary stages.

He also said the amplifiers were not for military use as reported by the newspaper as their frequency and power specifications meant they were more suitable for commercial purposes.

"The IME does not conduct classified military-related research," Lo said.

Lo also denied the newspaper's assertion that Todd was an expert on GaN, saying the American had joined IME as an entry level researcher with a group that focussed on the the design of sensors and actuators.

Todd had asked to be transferred to the GaN group which was just starting a research programme at the institute.

Indian scientist Susai Lawrence Selvaraj, who worked with the American at IME, said Todd "was never involved in any sensitive or highly confidential project or research".

"GaN research is not exclusive to the IME... GaN technology has, in fact, been thriving for many years in other countries where GaN technology is far more advanced than in Singapore," he told the inquiry.

"The IME-GaN group is not involved in any military projects with China."

Yuan Li, another scientist who worked with Todd, said the projects their group were working on "had no military applications because the speed of the device... was not fast enough".

A US congressional committee last year labelled Huawei and ZTE, another Chinese telecom firm, as potential security threats that should be excluded from US government contracts and barred from acquiring US firms.

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© 2013 AFP