JINAN, China -- Prosecutors in the trial of Bo Xilai, the fallen Communist Party star, said Sunday that Mr. Bo had bypassed important procedures in demoting his former police chief in the southwest metropolis of Chongqing after the chief confronted him with suspicions that Mr. Bo's wife had killed a British businessman.
The manner in which Mr. Bo replaced the police chief, Wang Lijun, is the basis of the abuse-of-power charge, one of three that Mr. Bo faces in the most closely watched trial in China in three decades. The prosecution cited testimony by a former head of the party organization department in Chongqing, Chen Cungen, saying that Mr. Bo had ordered Mr. Wang's removal despite the need for approval from the municipal party committee and the Ministry of Public Security.
Mr. Bo's defense lawyer said that Mr. Wang, who had helped Mr. Bo carry out a prominent and controversial anti-corruption campaign, was moved to another job in early 2012 because he was in poor health and suffering from mental strain. The lawyer called Mr. Wang an unreliable witness because Mr. Bo had slapped and fired Mr. Wang after he made the comments about Mr. Bo's wife. The lawyer also said that Mr. Wang had confronted Mr. Bo with the murder accusation simply to blackmail Mr. Bo.
The back-and-forth painted an ugly portrait of the internal workings of senior Communist Party officials, and it came one day after the dramatic high point of the trial, when Mr. Bo faced off with Mr. Wang, who brought down the charismatic party official when he fled to a nearby American consulate in February 2012.
It was the first time the two were known to have seen each other since Mr. Wang fled Chongqing, which Mr. Bo had governed for four years. In the consulate visit, which lasted more than 30 hours, Mr. Wang told American officials that Mr. Bo's wife, Gu Kailai, had poisoned the Briton, Neil Heywood, and that Mr. Bo was persecuting Mr. Wang because he knew about the killing.
In his testimony on Saturday, Mr. Bo took blame, to a degree, for the episode leading to Mr. Wang's flight.
"I made mistakes; I am very ashamed, and I am willing to take appropriate responsibility, but whether it's a crime or not a crime is another matter," Mr. Bo testified. He added that he had not bent the law to protect his wife because he did not believe that she had killed Mr. Heywood, and that he had demoted Mr. Wang right before he fled for the consulate because he believed that Mr. Wang was unstable.
Mr. Wang, who is serving 15 years for defection and other crimes, took the witness stand for the prosecution on Saturday. In glasses, a white shirt and neatly parted hair, he looked much as he did when he served as Mr. Bo's enforcer. Mr. Wang testified that Mr. Bo's wife secretly confessed to him on Nov. 14, 2011, that she had just poisoned Mr. Heywood. Mr. Wang was close to Ms. Gu and kept this a secret, but in late January 2012, he said, he told Mr. Bo that his wife had poisoned Mr. Heywood.
At a meeting the next day, he said, Mr. Bo chastised him in front of other officials and punched him in the face. "My body was shaking a bit," Mr. Wang said. "I discovered that the corner of my mouth was bleeding. Fluid was coming from my ears."
In his testimony, Mr. Bo said he had slapped Mr. Wang for what he thought were fabricated accusations about his wife. "I couldn't accept this. I was furious; I smashed a mug to the ground," Mr. Bo said.
On Sunday, Mr. Bo insisted again that he had slapped and not punched Mr. Wang. "I've never trained in boxing, and I don't have that kind of force," Mr. Bo said.
Besides the charge of abuse of power, Mr. Bo is also accused of taking bribes and embezzling amounts totaling 26.89 million renminbi, or $4.4 million. The abuse-of-power charge is the last one to be addressed in the trial, which began on Thursday and is expected to run at least through Monday. Mr. Bo has pleaded not guilty to all charges.
A populist politician and the son of a Communist revolutionary leader, Mr. Bo was dismissed from his post in March 2012. Soon afterward, the murder accusations became public. Ms. Gu was convicted of murder a year ago and given a suspended death sentence, essentially life in prison.
On Saturday, lurid Bo family secrets were laid bare to millions of fascinated Chinese who have been following the trial on a running court microblog that party officials set up in an effort to give the trial an air of legitimacy.
Earlier in the day, the defendant rejected accusations of embezzlement after a former colleague testified that Mr. Bo had arranged for Ms. Gu to accept 5 million renminbi of government money earmarked for a secret construction project in the early 2000s. Mr. Bo said that after his wife found out about an extramarital affair, she left for Britain with their son, Bo Guagua, and mostly lived there from 2000 to 2007, while their son was in school. Mr. Bo said Ms. Gu, a lawyer, had saved a lot of money -- 20 million to 30 million renminbi -- and his son had scholarships for his schooling, so he had no need to steal government money.
Mr. Bo's admission of adultery was immediately seized on by Chinese Web portals, one of which posted the headline "Bo Xilai Admits in Court Having Had an Affair, Wife Took Son Off to England in a Rage."
It was an example of how China's major state-approved news portals were presenting a unified voice to highlight the prosecution's evidence against Mr. Bo or, as in the case of the affair, to taint him with scandal.
In September, when the Communist Party announced its findings against Mr. Bo, it decided to include the accusation of adultery, saying he "had or maintained improper sexual relationships with a number of women." A Bo family associate said on Saturday that Mr. Bo and Ms. Gu both had affairs going back before 2000.
The associate and another person close to the Bo family who has been briefed on the trial proceedings said some of Mr. Bo's strongest assertions in court had been kept from the transcripts released on the court microblog. On Thursday, they said, Mr. Bo told the court that he had made one bribery confession last year to investigators only after being warned that his wife could be given the death sentence and his son, who had just graduated from Harvard, brought back to China to face charges.
"I felt like there were two other lives tethered to mine," Mr. Bo told the court, using a Chinese proverb.
Another detail left out of the transcripts on Friday also involved the pressure Mr. Bo said investigators had put on him, the two family associates said. They said he had testified that he had been interrogated hundreds of times and fainted 27 times.
Chinese news media coverage of the courtroom case on Saturday left no question that party authorities remained determined to dispense with Mr. Bo, who is expected to be sentenced to a long prison term. For three days now, no audio or video clips have been released in which Mr. Bo can be heard speaking. His statements are presented only via the transcripts.
An article on Saturday in The Legal Daily, an official newspaper under the guidance of the party's political and legal affairs committee, concluded that the testimony on the embezzlement charges "proves deliberate corruption on his part."
Patrick Zuo contributed research.
This article originally appeared in The New York Times.