Rick and Mary Todd have said they believe their son Shane was murdered because of his work for a Singapore institute with alleged links to a Chinese firm seen by the US as a security threat.

Mary Todd, 57, a church pastor, said they arrived a week before the start of the coroner's inquiry on May 13 to meet their lawyers, who have offered their services for free.

"We believe our son was murdered," she said, speaking to AFP on arrival at Changi Airport.

"Rick and I will be testifying. We're not sure about the rest at this point in time, but I know that my husband and myself will be (testifying)."

Lead lawyer Gloria James-Civetta, who met the Todds at the airport, said 63 witnesses are on the list although not all may be called to testify during the inquiry to determine the cause of death.

Shane Todd, an electronics engineer, was ending a stint as a researcher for the state-linked Institute of Microelectronics (IME) in Singapore and was preparing to return to the US when he was found dead in his apartment in June last year. He was 31.

His parents dispute a Singaporean autopsy report that he committed suicide.

The Singapore police and the US Federal Bureau of Investigation have been sharing information on the case.

Shane Todd was working on a project involving China's Huawei Technologies, although the IME and Huawei have said that talks on a joint collaboration did not progress beyond preliminary stages.

The IME has also said that it and Shane Todd were never involved in any secret research project and it has welcomed a US audit of its internal processes.

When asked about the fondest memory of her son, Mary Todd paused for a moment before saying: "It was all wonderful. He was a wonderful son. He was very bright, very funny, and loved by a lot."

She and her 58-year-old husband, an airline pilot, were met at the airport by their lawyer, some friends and a US embassy official.

Their three sons, one daughter-in-law, Mary's brother and Rick's sister will be flying down later this week to attend the inquest, Mary Todd said.

The coroner's inquiry or inquest is a legal process to determine the cause of death. Todd's family had been invited to attend and ask questions.