Agus Triyono & Rizky Amelia – The Anti-Corruption Court judges who controversially acquitted the suspended Bekasi mayor of graft charges are being investigated for possible ethical violations in the case, the Supreme Court revealed on Friday.

Hatta Ali, the deputy for supervision at the country's highest court, said the three judges – Azharyadi Pria Kusuma, Eka Suharta Winata Laksana and Ramlan Comel – were facing a probe and their ruling was also being evaluated to check for indications of wrongdoing.

The panel, serving at the Anti-Corruption Court in Bandung, ruled on Tuesday that Mochtar Mohammad was not guilty on four counts of embezzlement and bribery, in the process handing prosecutors from the Corruption Eradication Commission (KPK) their first-ever court loss.

In the wake of the verdict, there have been calls for a thorough investigation of the judges, in particular Ramlan. He was convicted of corruption in 2005 by the Pekanbaru District Court in Riau, and sentenced to two years in jail and fined Rp 100 million ($11,000). But the Riau High Court acquitted him the next year.

Hatta said the Supreme Court investigation was looking into whether any of the judges met Mochtar or his representatives outside the court, which would constitute an ethical violation.

"So far we haven't been able to conclude whether there were any such violations," he said. "We'll have to wait for the full results of the investigation."

Also on Friday, Busyro Muqoddas, the KPK chairman, called on the Supreme Court to enlist the help of academics when appointing judges to the Anti-Corruption Courts, to prevent those with poor track records serving on the bench.

"It's time for the Supreme Court to join hands with the academic community and the Judicial Commission in vetting future appointees more vigorously," he said.

He also said the Bandung case highlighted the importance of compiling a database of the country's judges, so that any past indiscretions or convictions would be immediately apparent.

Busyro said it was crucial that any judge serving in an Anti-Corruption Court be of impeccable integrity. "If a judge doesn't have integrity, this is the kind of mess we end up with," he said.

Hatta conceded that the Supreme Court had been unaware of Ramlan's conviction when it appointed him. "During the selection of ad hoc judges for the court, he failed to mention that he had previously been implicated in corruption," he said.

In 2006, however, the Supreme Court upheld Ramlan's acquittal, indicating it must have been aware of his track record.

While the Mochtar case is the first that the KPK has lost, it marks the 26th acquittal handed down by Anti-Corruption Courts across the country in the nine years they have operated. The 25 other cases were prosecuted by the Attorney General's Office.

The Bandung Anti-Corruption Court has come under particular scrutiny following Tuesday's verdict, having previously acquitted three other high-ranking regional officials.