O'Donnell, a foster parent known for supporting children's causes, called Miami attorney Jayne Weintraub two weeks ago and asked her to help win a new trial for Alex and Derek King, ages 13 and 14, Weintraub and O'Donnell's publicist told The Associated Press on Sunday.
Weintraub, a frequent cable television news commentator with more than 20 years experience trying murder cases, is representing Alex, she said. She said she is only representing one of the boys to avoid potential conflict issues; another attorney is representing Derek.
She declined to say how much O'Donnell was paying her.
"She hired them because she felt it was the right thing to do," said Cindi Berger, O'Donnell's publicist.
A judge tossed out the brothers' second-degree murder convictions on Thursday and ordered prosecutors and attorneys to try to settle the case through mediation before he signs an order for a new trial.
"The case was tugging at (O'Donnell's) heart strings. She was offended by what happened to these kids," Weintraub said.
O'Donnell sought to keep her role in the case private, Weintraub said, but the attorney said she was given clearance to discuss it after word of O'Donnell's involvement leaked late last week.
Weintraub, who counts rap mogul Sean "P. Diddy" Combs among her previous clients worked on the motion for a new trial, she said.
Alex and Derek were both a year younger when their father, Terry King, 40, was beaten to death with an aluminum baseball bat Nov. 26 while he slept at home in Cantonment.
A six-member jury concluded that an adult co-defendant, Ricky Chavis, wielded the weapon, but that the boys were accomplices by letting him in the house.
Chavis was acquitted of murder by a separate jury. He is also charged with molesting Alex.
By Alex Veiga