A gunman disguised as a lawyer shot dead Dhammika Amarasinghe as he was being escorted by prison guards to court in Colombo on Friday in connection with an unrelated case, police said.
Sri Lanka's cricket chief Thilanga Sumathipala was accused of aiding and abetting Amarasinghe, a man implicated in more than 28 murder cases, to obtain a forged passport and travel to London to witness a cricket match.
A police spokesman said the man who killed Amarasinghe had given himself up to the authorities. They said he carried out the attack to avenge Amarasinghe's alleged killing of another gang member in 2001.
"The latest shooting will have a direct bearing on the case against Sumathipala," a police spokesman said. With the killing of Amarasinghe, the prosecution becomes weak as he was the main witness who could have testified against Sumathipala, police said.
Sumathipala who heads the cricket's governing body has said the accusations against him were trumped up by his rivals in an effort to discredit him during the England tour last month.
Colombo-based businessman Sumathipala is also the chairman of Sri Lanka Telecom, the country's main telephone carrier which is 35 percent owned by Japan's NTT.
The case against Sumathipala is currently being heard by a magistrate. Sumathipala was ordered to appear before another magistrate on Thursday, but he said he was ill and unable to attend court as he had been admitted to a private hospital.
Sumathipala denies holing up