BALTIMORE, Md.—Kendell Richburg, a 36-year-old Baltimore police officer pleaded guilty March 11in U.S. District Court in Baltimore to helping a local drug dealer sell heroin and then robbing the dealer’s customers as part of a scheme that prosecutors said was a conspiracy to distribute heroin, cocaine and marijuana during a more than 18-month period that ended last year.

Richburg, who had been assigned to the Baltimore Police’s Violent Crimes Impact Section in the Northwestern District, was indicted by a federal grand jury on drug distribution and gun charges Jan. 17 after being suspended in November 2012 amid an FBI investigation. His identity was not revealed at the time of his suspension. The department only said that a plainclothes investigator had been suspended during an FBI probe.

According to federal prosecutors, Richburg, who lives in Baltimore, was involved in a conspiracy to distribute heroin, cocaine, crack cocaine and marijuana between January 2011 and October 2012. Prosecutors also alleged that Richburg was in illegal possession of two semi-automatic hand guns while engaged in drug trafficking.

The charges grew out of an investigation by Baltimore Police internal affairs investigators and the FBI. The grand jury’s findings were characterized as “deeply disturbing and represent an egregious violation of the sacred trust citizens place in police officers,” Baltimore Police Commissioner Anthony W. Batts said.

According to his plea agreement, Richburg sometimes returned to his co-conspirator some of the drugs seized from the drug purchasers so that the co-conspirator could re-sell the drugs. Prosecutors also said that Richburg falsified the arrest documents to eliminate the co-conspirator’s involvement, often falsely stating that Richburg had witnessed a drug transaction.

Richburg and the co-conspirator were also overheard discussing, in an FBI wiretap, the “planting” of evidence, and arranging an armed robbery. The electronic surveillance grew out of an FBI investigation of the sale of stolen iPads and iPhones.

Through the monitoring, investigators detailed that on Oct. 9, 2012, Richburg, armed with his service weapon, searched a person, without probable cause, and located a large amount of cash. The victim told Richburg that he had just received his paycheck. Richburg contacted his co-conspirator and arranged for the co-conspirator, whom Richburg knew was armed, to rob the victim, identifying where the victim was located.

Richburg faces a minimum mandatory sentence of five years in prison and a maximum of 40 years in prison for the drug conspiracy, and a minimum mandatory sentence of five years in prison, consecutive to any other sentence, and a maximum of life in prison for use of a firearm in relation to a drug trafficking crime. Sentencing is scheduled for June 11.