NEWARK — He spent a decade as a top prosecutor, trying murder cases in New Jersey, drug cases in federal court and a wide range of offenses in the military justice system.

He went on to become one of the state’s most prominent defense lawyers, representing clients as varied as Abu Ghraib defendants, the rap stars Lil’ Kim and Queen Latifah and members of Newark’s notorious street gangs.

But federal authorities charged Wednesday that the success their former colleague, Paul Bergrin, had in defending drug dealers and gang leaders was based on a brutal calculus that he had boiled down to a phrase he repeated like a slogan: No witnesses, no case.

In an indictment unsealed on Wednesday in United States District Court in Newark, prosecutors accused Mr. Bergrin, 53, of orchestrating the murder of a confidential witness by leaking his name to drug dealers who shot him in broad daylight on a Newark street corner; of traveling to Chicago to hire a murderer to kill a witness in another case; of coaching some eyewitnesses to lie; and of paying others to change their stories or leave town on the day they were to testify.

To prosecutors, the charges are the latest example of the deadly challenge they face protecting witnesses at a time when the criminal justice system has few resources to shield them and the prevailing street code in many cities urges civilians to “stop snitching.”