Associated Press in Jakarta – Police in the Indonesian capital were yesterday questioning 18 witnesses and working with intelligence agencies to determine whether deposed president Suharto's youngest son was involved in the assassination of a prominent judge.

"There is no proof of that. It's only speculation," said Hutomo "Tommy" Mandala Putra's lawyer, Erman Umar, adding he had not seen his client since November.

Thursday's assassination of Supreme Court justice Syaifuddin Kartasasita came just eight months after he sent Hutomo to prison for corruption.

Police spokesman Lieutenant Colonel Anton Barul Alam said detectives were also looking into whether Mohamad "Bob" Hasan, a millionaire businessman and Suharto crony – whom Syaifuddin sentenced earlier this year to six years in jail on a remote penal island – was linked to the killing. "As a judge, there were many people who did not like him," Colonel Alam said.

Four men on motorbikes rode up alongside a vehicle driven by Syaifuddin, Indonesia's second-most senior judge, on Thursday, and fired four shots, fatally wounding the 61-year-old.

Most newspapers yesterday described the judge as one of a rare breed among Indonesia's graft-ridden judiciary – a man who was personally incorruptible. However, the Koran Tempo newspaper reported allegations that the dead judge had taken bribes in an unrelated case.

Syaifuddin was the presiding Supreme Court judge who sentenced Suharto's son last September to 18 months in jail for his part in a multimillion-dollar land scam.

Using legal stalling tactics, the millionaire playboy was not jailed immediately and disappeared in November when an arrest warrant was issued. Since then, Hutomo has been blamed for several outbreaks of violence that have stirred tensions in crisis-ridden Indonesia.

If the judge's killing "is not solved quickly, we are in deep trouble. It sends a clear message that one can get away with attacking law enforcement," said former attorney-general Marzuki Darusman.