BEIJING — Gu Kailai, the wife of one of China’s most ambitious leaders, plotted with allies, including the local police chief, to protect her son from what she saw as the blackmail demands of the British business associate she confessed in court to killing, according to accounts of the trial that emerged on Friday, including one from the state-run Xinhua news agency.

Prosecutors presented evidence at the trial on Thursday that the Briton, Neil Heywood, had demanded tens of millions of dollars from Ms. Gu’s son, locked him up in a residence in England and sent an e-mail threatening to “destroy” him. In response, prosecutors said, Ms. Gu sought help from the local police chief, who refused to go along with her plan to get rid of Mr. Heywood and secretly recorded her confession to him on the day after she poisoned Mr. Heywood.

The tale was designed to give a rare glimpse into the darkest corners of a Chinese ruling family and its foreign ties. While it was impossible to confirm details independently, the prosecution’s case portrayed a dramatic struggle between Ms. Gu, 53; her Oxford- and Harvard-educated son, Bo Guagua, 24; and Mr. Heywood, 41, a longtime friend and business associate whose body was found in November in a hotel in Chongqing, the fog-wreathed central China metropolis governed for more than four years by Ms. Gu’s husband, Bo Xilai, a Politburo member.

Ms. Gu and a family aide, Zhang Xiaojun, stood trial on Thursday in Hefei, Anhui Province. No verdict was delivered, but a court official said the defendants did not object to the charges. The details of the court arguments that emerged Friday were not included in a terse statement issued the previous day by officials.