Juan Carter was a dirty police officer, prosecutors say, who took guns from criminals and then sold them or gave them to his friends. Defense attorneys say he was merely a “fall guy,” a low-level officer made to take the blame for systemic problems with a gun task force.

Twelve Prince George’s County jurors will try to decide whether Carter, a Prince George’s County narcotics detective, committed theft and misconduct in office while assigned to the state police-led task force in 2008 and 2009.

Carter’s first trial on the same charges ended in a mistrial last year after jurors could not reach a verdict. On Wednesday, prosecutors and defense attorneys seemed to sharpen their pitches during opening statements in his new trial.

Assistant State’s Attorney Renee Joy slowly read Carter’s oath as a police officer before turning to the allegations against him, telling jurors that more than 20 firearms seized by Carter never made it to the police department’s property room. Two, Joy said, were later recovered from a convicted felon, a friend of Carter’s, during an undercover gun-buying operation.

Joy said Carter, a senior corporal on a group dedicated to seizing firearms from criminals, reduced himself to “nothing more than a street-level gun dealer.”

Doug Wood, Carter’s defense attorney, called Carter a “dedicated police officer” who was charged with criminal misconduct after investigators found record-keeping and other problems with the gun task force to which he was assigned.

Although he acknowledged that Carter, 38, “wasn’t keeping the appropriate amount of paperwork” on the weapons he seized, Wood said that was “the mode of operation of the task force.” He said Carter also had some weapons stolen out of his police van.

“You had to have a fall guy, and it had to be Juan Carter,” Wood said.

The two sides have made most of same assertions since Carter’s indictment in 2010. Police have also said one of the guns Carter was supposed to have seized was used in the September 2009 shooting of an off-duty Prince George’s police officer, Eric Horne, when two men tried to carjack Horne’s vehicle.

It remains unclear how many guns Carter might have taken, lost or sold because some have not been recovered, authorities have said.

Carter was suspended without pay after his 2010 indictment.

Wednesday’s dramatic opening statements gave way to more-tedious testimony, as prosecutors and defense attorneys questioned witnesses about the proper procedures for gun seizure and storage. Prosecutors highlighted Carter’s role as the senior corporal in charge of property; defense attorneys asked about other supervisors in the unit and the security of the facility in which seized guns are stored.

The trial is expected to last through the week.