SPRINGFIELD, Ill. • The Illinois Supreme Court says video has become so common in law enforcement that police must preserve it as evidence even in misdemeanor cases.

The court upheld sanctions today in a case where police erased video of a drunken driving arrest. The defendant told prosecutors she intended to fight the charges and wanted the video, but police still followed their policy of destroying videos after 30 days.

As punishment, the trial judge barred the arresting officer from testifying about anything that took place when his squad-car camera was running.

Cook County prosecutors appealed, saying that would cripple their case.

But the Supreme Court says the video should have been saved and the judge was within his rights to limit testimony when that didn't happen.