Years of video evidence gathered by the Atlanta police, most of it from in-car video systems was lost in a March ransomware attack.
The footage was "lost and cannot be recovered", said Atlanta Police Chief Erika Shields.
More than 140 separate applications were totally or partially disabled by the attack, said Daphne Rackley who heads Atlanta's IT department. About 30% of the affected programs were "mission critical" as they were used by either the police or its courts, the BBC reports.
Shields told the Atlanta Journal Constitution that despite losing the video recordings, no "crucial evidence" had been compromised, as other evidence such as the testimony of an officer would "make or break" a case.