Defense lawyer Richard Rubin said in his opening statement that Strickland would testify that his wife took Haleigh to doctors weekly and told him the girl was causing her own cuts, bruises and other injuries.
"He believed what he was told, and that was that Haleigh was a self-abuser, a child that did things to herself that caused injury," Rubin said.
Strickland, 34, faces six assault and battery charges for the injuries Haleigh suffered in September 2005 and from earlier beatings from a bat, his foot, a plastic stick and his open hand.
Prosecutors said Strickland beat the girl with his wife, Holli Strickland. She died in an apparent murder-suicide with her grandmother days after being charged.
Haleigh's sister, then-9-year-old Samantha Poutre, originally told authorities that her sister hit her head on a pipe while doing gymnastics.
The child, now 12, has come forward to say she saw Jason Strickland push her sister, Brandt said.
Samantha said Holli and Jason Strickland had told her to "make up a story" about what happened, Brandt told jurors.
Haleigh was adopted at age 7 by Holli Strickland, her aunt.
After the brain injury she suffered at age 11, Haleigh was comatose. Her case led to a right-to-die battle, and she was nearly removed from life support before she suddenly began breathing on her own. She remains in a rehabilitation center.