The DeKalb County Police Department has expanded its internal affairs division to investigate some of the officer misconduct cases that plagued the agency recently.

Since January, nearly a dozen officers have been arrested or fired or have resigned in lieu of termination as a result of probes into wrongdoing or serious policy violations.

"We take allegations of misconduct very serious and will not hesitate to take action, even when it's our own," DeKalb Police Chief William O'Brien told The Atlanta Journal-Constitution in an interview Tuesday morning.

Late Tuesday afternoon, DeKalb Police Sgt. Jerry Banks, who's married, was fired for obstructing fellow officers' attempts to serve a search warrant at the home of a woman with whom he shared an undefined relationship.

"An internal affairs investigation deemed Banks violated departmental policies of conduct unbecoming [an officer] and violation of the law," DeKalb police spokeswoman Mekka Parish said.

And last week, DeKalb Police Capt. Suzanne Kaulbach was fired after being arrested in June on allegations that she kept stolen property at her Clayton County home.

O'Brien stopped short of calling the new internal affairs members a special task force within the IA division, but said he added the new members — a sergeant and two officers — two months ago.

Parish said the new staff was not involved in the investigations that led to Kaulbach's ouster, but it is unclear if they investigated Banks.

Frank Rotondo, executive director of the Georgia Association of Chiefs of Police, applauded O'Brien's move.

"I wish more departments would enhance internal affairs," Rotondo said Tuesday by phone. "If the standards become lax, the department becomes a slipshod operation."

He said O'Brien, who is in his second year as chief, owes it to DeKalb citizens to do everything to protect them and their investment in policing the county.

"An officer who [steps out of line] could cost taxpayers money in the way of lawsuits," Rotondo said.

That is a very real possibility in the case of former officers Blake Andrew Norwood and Arthur Parker III and former Sgt. Anthony Remone Robinson, who were indicted and arrested in May on charges that they beat four handcuffed teens last year and in 2010.

Three of the victims were juveniles, DeKalb County prosecutors said, and the fourth is suing the Police Department and the county.

Typically, internal affairs investigates complaints against officers ranging from rudeness to excessive force. The division, which had run with four officers and five detectives, also looks into all incidents in which an officer discharges his or her weapon.

O'Brien said the added officers have so far only opened investigations into officers who have been arrested or charged.

Once those cases are concluded, though, the additional officers can open their own investigations as they see fit, O'Brien said.

"They will be looking into even rumors, if they think it's warranted," he said. "We won't be chasing rabbits just because we can, but we do want to get out in front of these kinds of allegations."