"When I read the note I handed it back to the officer and I said my son may have killed himself, but he did not write this note," Mary Todd said of meeting with authorities in Singapore last year.
The couple also found no evidence of a pulley system: there were no pulleys or holes in the ceramic walls in the bathroom, Mary Todd said.
Shane Todd's apartment appeared as if he were about to return to the United States: clean clothes were folded and boxes packed. A plane ticket sat on the table. He also had a new job lined up, the family said.
Holding a doctorate in electrical engineering, Shane Todd worked for his prominent employer, helping to develop faster, more powerful semiconductors by using the compound gallium nitride.
In his last months, Todd expressed stress about his work and even fear for his life, his family said. He wondered if his work might be illegal or a risk to U.S. national security, his parents said.
After his death, Todd's parents found that his hard drive contained a proposal between the Singapore outfit and a prominent Chinese telecom firm, Huawei, to build a powerful amplifier using gallium nitride technology.
The Todds showed the documents to CNN.
Huawei has been at the center of controversy.
It and another Chinese telecom company, ZTE, were cited last October by the U.S. House Intelligence Committee, which said the two firms "cannot be trusted to be free of foreign state influence and thus pose a security threat to the United States and to our systems."
That comment referred to the firms' business practices, and the committee report said, "the United States should view with suspicion the continued threat of the U.S. telecommunications market" by the Chinese companies.
Huawei rejected the committee report, calling the findings "baseless."
In reference to the proposal found on Todd's hard drive, Huawei and the Institute of Microelectronics in Singapore insisted they had no such project or even a business relationship, though they acknowledged preliminary talks.
Nothing became of those talks, they said.
"There is speculation by the Todd family that Shane's death was related to a project undertaken by IME with Huawei. Neither IME nor Shane was involved in any classified research project," IME said in a statement.
"The research and development carried out in IME is to advance economic growth for Singapore and deliver on healthcare and social benefits," it said.
IME isn't commenting further because Todd's death is under police investigation. "IME has cooperated fully with the authorities and will continue to do so," the institute said.
Huawei spokesman Scott Sykes said that gallium nitride, or GaN, technology improves power amplifier efficiency and is "widely recognized as a key technology for next-generation wireless base stations."
"IME approached Huawei on one occasion to cooperate with them in the GaN field, but we decided not to accept, and consequently do not have any cooperation with IME related to GaN," Sykes said in a statement to CNN.
The Singapore police have said they received "no response" from the Todd family to share evidence, including the hard drive.
"If they were not comfortable handing evidence in their possession to the Singapore Police Force (SPF), they could seek the FBI's help to review the evidence," a spokesman said. "As there has so far been no response to this request, SPF has sought the FBI's assistance to engage the family and for FBI to examine the evidence."