Hearing-impaired people tuning in to a news conference about the arrest of a suspected serial killer got a message of gibberish from an American Sign Language interpreter.As Tampa police Chief Brian Dugan announced the arrest of Howell Donaldson Wednesday night, interpreter Derlyn Roberts was there beside him, making signs that made no sense."She sat up there and waved her arms like she was singing Jingle Bells," Rachell Settambrino, who is deaf and teaches American Sign Language at the University of South Florida, told the Tampa Bay Times through an interpreter.