Yeah, Hammurabi was probably tired of having to constantly adjudicate disputes between clans, so his top priority was probably to shut down most complaints from the get go.
Hammurabi didn't adjudicate things himself, despite popular belief (based on stories about King Solomon?). His kingdom had a panel of judges to hear cases -- and the Code had laws to keep them honest. Apparently, the judges often ignored the code in their rulings, however, indicating that judicial corruption is as old as civilization itself.
But yes, not burdening the judiciary with frivolous trials is as good a reason for a high evidentiary standard as seeing that justice is done and the innocent not unfairly prosecuted. Part of the reason for the infamous Japanese high conviction rate, for example, is because the Japanese system won't bother to arrest or charge you unless their case is very solid.
