FORT MYERS, Fla. (AP) _ A murder defendant burst into tears as recorded voices of relatives he is accused of killing filled a hushed courtroom.

Steven Benson, 35, wept for several minutes after hearing his mother and adopted brother in a heated exchange over a mess made by the dog.

Benson is accused of planting two pipe bombs that killed his mother, 63- year-old Lancaster Leaf Co. tobacco heiress Margaret Benson, and his adopted brother Scott Benson, 21, on July 9, 1985.

The tape-recording, and testimony by Mrs. Benson's secretary Joyce Quinn were an attempt by defense attorneys to portray Scott as the target of the bombing by an unknown person because of his alleged drug use.

Ms. Quinn testified that Scott threatened five times to kill his mother on the day in June 1983 when the tape-recording was made.

''Suddenly, Scott comes out of the room and tells Margaret he can have the dog kill her if he wants to,'' Ms. Quinn testified. ''At one point he ran to her, grabbed her by the arms and says if she ever does it again he's going to have the dog kill her.''

Ms. Quinn also testified that she heard Scott in his room earlier inhaling deeply, and police found two apparently empty nitrous oxide canisters in his room.

The officers were at the Benson's posh Naples home to take Scott into custody under the Baker Act as a threat to himself or others.

Steven Benson, who is also charged with attempted murder because his sister, Carol Benson Kendall, 42, was badly burned in the blasts, could be sentenced to death in the electric chair or life in prison if convicted.

Meanwhile, authorities said late Tuesday that Guido Luis Dal Molin Jr., 22, an electronics wizard charged with a January shooting death, was back in custody after escaping from the Collier County jail early Saturday by outsmarting guards with their own electronic equipment.

Dal Molin, who also had been subpoenaed as a defense witness in Benson's murder trial, apparently had been living in the woods since he jammed his cell lock, ran past guards to a control room and pushed buttons to strand the guards and open doors for himself, said Collier County Sheriff's Lt. Eric Daniels.

Off-duty Deputy Tom Fife spotted Dal Molin about 2 1/2 miles from the jail and detained him.