For the second time this week, a Prince George's County judge has denied bond to two Adelphi teen-agers accused of the first degree murder of the father of one of them.

While acknowledging the two defendants were presumed innocent until proven guilty, District Judge Louis J. DiTrani told lawyers representing Lisa Ann Casella, 15, and Daniel Eric Reedy, 14, that "we know there is a confession . . . that Lisa Casella had contracted with the codefendant . . . for the murder of both the father and the mother. That's in the statement of probable cause filed by police based on a written confession."

Joseph F. Vallario Jr., representing Casella, told DiTrani that his client plans to argue that she went to assist her father, Emilio Casella, when he was knifed to death last Thursday, and did not ask two neighborhood friends to kill him for$5,000, as prosecutors have claimed.

Reedy's mother, Gloria Reedy, told DiTrani during yesterday's hearing that her son had never been in trouble with the law before. She said he had not been attending school recently because of a heart condition and "emotional problems" following the death of her other son last September.

DiTrani said the two teen-agers, if released, could pose a danger to Casella's mother, who was slightly injured in the incident. "To release them to the community would be irresponsible," DiTrani said. "It's a dastardly crime, it's the worst type of crime."

He said the alleged offense "would indicate an unstable personality. I don't want it on my conscience if they are back out there and someone else gets hurt."

A third defendant, Fred Allan Mozingo, 19, is also being held without bond in the county detention center.