Michael Taylor was testifying Tuesday in the trial of his friends, twins Travers and Tremayne Johnson, The Baltimore Sun reported.
The twins are accused of setting a pit bull named Phoenix on fire May 27, 2009.
Prosecutors interrupted Taylor as he was answering defense questions, raising Fifth Amendment concerns. The court called in his attorney before letting him go on.
The defense said Taylor matched the description of a man seen running from the scene. He repeatedly said he did not want to testify and that he had lied to police earlier.
Defense attorneys tangled with police Sgt. Jarron Jackson, who handled the investigation, trying to make him admit officers failed to investigate other suspects and did not test some clothing for chemicals.