Lawyers fear a measure intended to cut district court waiting times could lead to miscarriages of justice.
Changes to the current depositions hearing process, under the Criminal Procedure Bill, will be introduced in the second half of 2009.
The changes mean a committal hearing will be carried out in written form, rather than as oral evidence, unless an oral evidence hearing is applied for.
The Ministry of Justice says this should eventually translate into trials proceeding at a faster rate. But the president of the Criminal Bar Association, Anthony Rogers, says without oral questioning, important evidence may be missed.
He says if critical evidence comes out only at the trial stage, it could lead to an aborted trial and further delays.