Bo Guagua, son of sacked Chinese politician Bo Xilai, says the “facts will speak for themselves” when his mother, Gu Kailai, goes on trial for murder.
Bo Guagua said in an e-mail to US broadcaster CNN that he had given a witness statement to Gu Kailai’s defence team.
Gu Kailai will be tried by a court in Hefei on Thursday for the murder of British businessman Neil Heywood.
The case has become one of China’s biggest political scandals in decades.
Gu Kailai, a well-known lawyer, and her aide Zhang Xiaojun are accused of killing Neil Heywood in November 2011 in the city of Chongqing, where Bo Xilai was Communist Party chief.
State media said Gu Kailai and her son fell out with Neil Heywood over “economic interests” and that she was worried about “Neil Heywood’s threat to her son’s personal security”.
“As I was cited as a motivating factor for the crimes accused of my mother, I have already submitted my witness statement,” Bo Guagua told CNN.
“I hope that my mother will have the opportunity to review them,” the 24-year-old said.
Bo Guagua, who is believed to be in the US after graduating from Harvard University, did not specify what he wrote in his statement, CNN reports.
State media has called the case against Gu Kailai and her aide “irrefutable and substantial”. She has not been seen in public since April, when the investigation was announced.
British diplomats will be allowed to witness the trial but journalists will not be attending. Gu Kailai is being represented by state-appointed lawyers.
The case comes as China prepares to install a new generation of top leaders at a party congress due later this year, in its 10-yearly leadership transition.
Bo Xilai, who has been sacked from his official positions, had been seen as a strong contender for promotion. He has not been seen in public since April.