ATLANTA - At least 51 Atlanta police officers were found to lack the authority to make arrests because they hadn't met state requirements for training, department officials said.

Since 1990, state law has required law enforcement officers to get at least 20 hours of training each year covering policies, work-related computer programs or forms officers must fill out. Since 2006, at least one of those hours must be on the use of firearms and another must focus on use of force.

"We're going back through each individual file to make sure everything is in place," Atlanta Police Chief George Turner told WGCL-TV.

The Atlanta Journal-Constitution reported that seven officers are on administrative duty pending resolution of the issue, 19 have brought their training up to date and 25 are still being notified. Maj. Jeff Glazier, commander of the Atlanta police training academy, said Thursday the department still has about 600 officer files to review.

The problem was discovered a year ago when academy staff were reviewing the files of officers returning to duty after being away for extended periods.

"The APD administration's failures have just compromised a ton of criminal convictions and pending cases," said a past president of the Georgia Association of Criminal Defense Lawyers, Christine A. Koehler.

Some cases involving the officers are two decades old, police officials said. "We don't know what the impact will be," Glazier said.

Koehler said defense attorneys who handle APD cases have been informed "about the lack of certification so our lawyers will know what to look for, so they'll know to raise issues with these officers illegally" making arrests.

Fulton District Attorney Paul Howard, whose office prosecutes Atlanta cases, said an arrest or conviction "is not automatically overturned because a police officer's certification has expired. Individual, case-by-case analysis of each criminal matter must take place before such a determination is made."

Turner and Glazier said it did not mean the officers were not certified if they did not have the authority to make arrests.