INDIANAPOLIS -- Prosecutors began dropping charges Tuesday in at least 20 drug cases because three narcotics detectives are among four city police officers arrested this month.

The dismissals by the Marion County Prosecutor's Office came one day after Detective Jason Barber made his initial court appearance on state charges of selling a handgun to a felon and official misconduct.

More dismissals were expected, said prosecutor's office spokesman Matthew Symons.

Two weeks ago, the FBI arrested two other narcotics detectives, Robert Long and Jason Edwards, and a patrol officer, James Davis, after federal prosecutors secured indictments against them on charges of stealing money and marijuana from drug dealers and selling the drugs through a third party. The three also face firearms charges.

Barber was in jail awaiting a bond reduction hearing Wednesday. Long, Edwards and Davis were in federal custody pending trial, said U.S. Attorney spokeswoman Mary Bippus.

"Every single one of them, every single case that these officers are on, has become less strong," Marion County Prosecutor Carl Brizzi said after Barber's court appearance. "We will probably wind up dismissing several of those cases if all we have is the (testimony of) one narcotics officer who's been charged, because we'll lose those cases," he said.

Deputy Prosecutor Lawrence Brodeur said he was evaluating 12 other cases and would look at others in the coming days.

Barber worked with Long and Edwards in the dangerous drug unit of the Indianapolis Metropolitan Police Department but has not been linked to the pair's alleged crimes. Barber was arrested at his home Friday.

The arrests have tainted the credibility of the roughly 1,700-member IMPD force in the eyes of the public, Brizzi said.

"It hurts every jury trial that we try over the next several months," Brizzi said.

Ralph Staples Jr., an attorney for Long, said prosecutors' decision to drop charges in some drug deals was up to their discretion. He said his client has pleaded not guilty to the charges against him.

The Associated Press left messages Tuesday for attorneys representing Edwards and Davis.

Brizzi, defense attorney Robert Hammerle and other experts said the arrests could lead to successful appeals for some people already serving prison sentences based on the work of the arrested officers.

It remained unclear Tuesday how many convictions were threatened, Symons said.

Hammerle represented Bobby D. Johnson, 33, who was arrested in November on charges of marijuana possession and a firearms violation. Johnson's case was among those to be dismissed Tuesday.

"This is horrifying," Hammerle said. "I don't want to sit here and represent that my guy was a choir director ... (but) the guys with the badges are the crooks."

Hammerle said he thinks federal authorities should be brought in to investigate the entire IMPD narcotics branch. A metro police spokesperson said Tuesday that Chief Michael Spears does not intend to request federal assistance.