Gu Kailai has admitted murdering British businessman Neil Heywood and blamed her actions on a mental breakdown, Chinese state media report.
The Xinhua news agency reports Ms Gu, the wife of former top politician Bo Xilai, said she would "accept and calmly face any sentence".
Ms Gu was charged with the murder of Mr Heywood in a one-day trial on Thursday.
Mr Heywood was found dead in the city of Chongqing in November 2011.
The Xinhua report said that Ms Gu had addressed the court towards the end of its session, and said: "Those few days last November, when I saw how my son was in danger, I suffered a nervous breakdown. A tragedy happened because of me".
Earlier on Friday, four senior police officers admitted covering up evidence linking Ms Gu to the murder, a court official said.
The dates for the verdicts in both trials are yet to be announced.
The case appears to have ended the career of Chongqing's ex-leader Bo Xilai, who had been seen as a likely candidate for a top job in the leadership transition due later this year.
Seven members of the nine-strong politburo Standing Committee are due to retire, paving the way for a new generation of leaders.
But former high-flier Mr Bo, a populist and an ambitious politician, has not been seen in public since the investigation into his wife was announced.