A federal judge on Thursday tacked 18 months onto the 10-year prison term being served by a top associate of convicted drug kingpin Kaboni Savage for conspiring with Savage to threaten witnesses.

"It's no secret we have a big problem in Philadelphia with people being afraid to testify. They're scared to death," U.S. District Judge Norma L. Shapiro told Dawud Bey.

Bey, 41, a member of a family notorious in South Philadelphia for violent drug dealing, told Shapiro that his time in prison so far had changed him.

While serving a 2006 drug-dealing sentence, Bey said, he has earned a high school diploma and completed drug- and alcohol-abuse and anger-management courses.

"My past is no longer part of my future," added Bey, who pleaded guilty to witness-intimidation conspiracy in March.

The judge said that she was impressed by Bey's prison accomplishments, and that his onetime job managing real estate showed he could succeed. But Shapiro said she was troubled by Bey's misconduct in prison, which cost him the opportunity to deduct 179 days from his sentence.

Prison officials "don't think you're a law-abiding citizen yet," Shapiro said. "The question is what conditions would help you lead a law-abiding life? It's obvious, if you want to, you could."

Assistant U.S. Attorney David E. Troyer argued that Bey should serve 33 to 41 months in prison after his current term, which is set to end in July 2013.

"His threats terrorized these witnesses," Troyer said. Bey's conduct, he said, was even more brazen because Savage and Bey planned the threats while in federal custody by scooping water from their cell toilet bowls and talking through the plumbing.

In 2004, the pair were being held for trial on the drug-conspiracy indictment. Bey pleaded guilty and was sentenced to 10 years; Savage was convicted at trial and is serving a 30-year term.

Last year, Savage and three associates were charged in a federal racketeering indictment with 12 murders, seven tied to witness intimidation. Prosecutors are considering seeking the death penalty.

Defense attorney Arnold C. Joseph argued that any sentence should be served at the same time as his current prison term. He accused prosecutors of "manipulation" for trying to tar Bey with Savage's alleged homicides.

Ultimately, Shapiro split the difference, sentencing Bey to 36 months, but making only 18 after his current term.