Mismanagement and understaffing are blamed.
Findings of an internal affairs investigation released cite hundreds of pieces of evidence that weren't put into evidence storage and instead were left in offices or taken home by detectives.
Arpaio apologized for the bungled cases and has since said his office has moved to clear up the inadequately investigated cases and has taken steps to prevent the problem from happening again.
More than 400 cases slipped through the cracks.
