A court official in China says four policemen have admitted covering up the murder of Briton Neil Heywood, a day after the wife of a former top politician was tried for the killing.
Mr Heywood was found dead in the city of Chongqing in November 2011.
The court official told reporters the senior officers had hidden evidence linking Gu Kailai, wife of Chongqing's ex-leader Bo Xilai, to the case.
Ms Gu was charged with the murder of Mr Heywood in a one-day trial on Thursday.
She did not contest the charges, according to a court official.
The dates for the verdicts in both trials are yet to be announced.
The case appears to have ended the career of 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.
The four police officers were charged with covering up Ms Gu's actions and "bending the law to achieve personal benefit", Tang Yigan, an official with the Hefei Intermediate Court in eastern China, told reporters.
The four include Guo Weiguo, former deputy chief of Chongqing's Public Security Bureau, and Li Yang, former chief of the bureau's criminal section, Xinhua news agency said.
The other two officers were named as Wang Pengfei and Wang Zhi.
Foreign journalists seeking to attend the police officers' trial could not get in.
The court official did not specify why the officers had sought to cover up the murder and made no mention of Mr Bo, the Reuters news agency reported.
Mr Heywood's death was initially recorded as a heart attack. But the case was reopened after Chongqing's top security official - police chief Wang Lijun - fled to the US consulate in Chengdu, reportedly with information that the Briton had been murdered.
Speaking after Ms Gu's trial on Thursday, Mr Tang said she and her aide Zhang Xiaojun - who was also charged - "did not raise objections to the facts and the charges".
The prosecution alleged Ms Gu had been involved in a business dispute with Mr Heywood, and believed he had "threatened the personal safety of her son... and decided to kill him", Mr Tang said, reading from a statement.
"After Heywood became intoxicated, vomited and asked for a drink of water, she poured a poison into his mouth that had been prepared beforehand and that she had given to Zhang Xiaojun to bring along, causing Heywood's death," he said in the statement.
A formal verdict is to be delivered at a later date, the court said. Both face the death penalty if convicted but many observers say the suggestion that Ms Gu was protecting her son could be used as a justification for a degree of leniency.
Mr Heywood's relatives have not commented on the case and nor has the UK Foreign Office. Two British diplomats were allowed to witness the trial but no foreign journalists were allowed in.
Wang Lijun, who was once Bo Xilai's right-hand man, has not been seen in public since his flight to the US consulate in February.
The South China Morning Post, citing an unidentified source, said Mr Wang was expected to go on trial in Chengdu in the coming days.
How the party will handle Mr Bo, who has been sacked from his posts, remains unclear.
This scandal risked tainting the inner sanctum of the Communist Party just as it embarked on a delicate political transition to a new party leadership, reports the BBC's diplomatic correspondent Bridget Kendall.
Reporting of the case is being tightly controlled in Chinese media.
Comment on Twitter-like microblogs was also being tightly controlled, with all the key names in the case banned as keywords.