"It's to ferret out corruption we might have inside," said James P. O'Neill, director of the detention center. But because the detention center on any given day ranges from 1,300 to 1,400 inmates, who have access to 80 phones from 8 a.m. to 10 p.m., not all calls are necessarily monitored.

Calls from attorneys are not recorded, either. O'Neil said all lawyers registered with the state bar association are omitted from recordings.

Last month, 19-year-old Sterlin Matthews was convicted of killing a 16-year-old on Halloween in 2008. It was the second time Baltimore County prosecutors tried the teen, after his first trial ended in a hung jury. Prosecutors were challenged by the lack of physical evidence linking Matthews to the shooting and uncooperative witnesses; the killer had been wearing a mask.

Buie, Matthews' defense attorney, said after the trial that prosecutors "really did not know who committed the crime." The jail calls, "sunk our ship," he said.

County prosecutors William B. Bickel and Danielle Williams built a case around recordings of Matthews' phone calls from the detention center, in which he is recorded telling friends about the witnesses to keep them from coming to court.

The jury took less than an hour to convict Matthews of second degree murder and related charges. His sentencing is scheduled for January.

"When you have a witness that says one thing to the police and then changes the story, if you can give an explanation, mainly a threat, then the jury will understand more," Shellenberger said. "I think it was very helpful to give the jury context."

When the trial was supposed to begin in mid-October, prosecutors said, the witness who identified Matthews in the shooting did not show up in court. She had previously identified Matthews to police as the masked teen who had been seen by the victim's friends just before the shooting. Officials began to suspect witness intimidation.

Prosecutors said Matthews intentionally used another inmate's ID number, which must be entered in order for inmates to make outgoing calls, to make it difficult for investigators to listen in on his conversations.

Homicide detective Alvin Barton also testified that he received a call from the witness saying she was too scared shortly before she was supposed to testify.

Matthews was also heard speaking to a friend through a wall, inside an interview room at police headquarters. All six of the interview rooms used by homicide detectives have surveillance cameras to record interviews with detectives.

When the detective left the room, Matthews is recorded speaking to one of his friends through the wall, saying his friend needed to "holler at them," which prosecutors said was an attempt to deter the witness from testifying.

jkanderson@baltsun.com

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