The South Australian Court of Criminal Appeal today unanimously rejected a bid by lawyer Eugene McGee and his brother Craig for a permanent stay of proceedings.

Charged with conspiracy to attempt to pervert the course of justice, the brothers had gone to the court arguing that the charge did not exist under South Australian law.

However, the court ruled the offence was properly constituted.

"The essence of the offence is the doing of an act which has a tendency and is intended to pervert the administration of justice," Chief Justice John Doyle said in his reasons.

"Accordingly, there can be a conspiracy to commit such an offence."

It has been alleged the McGee brothers obstructed a police investigation into Eugene McGee's involvement in a hit-and-run crash in 2003 which killed cyclist Ian Humphrey.

A former police prosecutor, Eugene McGee was previously found guilty of driving without due care on the night he hit and killed Mr Humphrey and fled the scene.

He was fined $3100 and disqualified from driving for 12 months.

The lawyer and his brother were charged with conspiracy to attempt to pervert the course of justice following a subsequent royal commission into the police investigation of the crash.

They now face a District Court trial on the charges, probably some time in 2009.