I'm not sure TM is trying to take the fall for MM. I no longer feel he is that emotionally invested in his daughter...if he ever was.
Since I believe that he is an easy liar, I was puzzled at his denial of DV. Why not throw MM a lifeline? In the opening statement, before his hatred was revealed by witnesses, his lawyer seemed to be suggesting that he and JC weregolfing buddies! "Hey, lets visit ole Jason, Molly and the kids.Fun times ahead."
He never visited his daughter in four years. He wasn't happy with her choice of husband, though, in fact...it was MM who "married up." Her husband was an executive...TM one of a group of agents, never having climbed the ladder of success much in the FBI. He even had to take money from this rowdy son-in-law so he could host a wedding to impress his friends...which he alone could not afford.
I don't think TM was too thrilled with the chaos that MM brought into his life. I think he'd been angry about MM involving her Mother in her issues...and then SM would drag him in. I bet it was SM that insisted they drive down. SM probably wanted him to fix MM's marriage be abuse if not...she's back in their laps again.
I don't think there even needed to be a big dramatic trigger that night. I think TM had been seething for a long time over lots of issues. It could be something as simple as their arguing woke him up after a long weary drive...and he grabbed the bat, furious and tired. "I'll put a stop to this or I'll call the cops!"
He walks in, slams JC in the back of the head....just keeps going and MM in her fury...joins the beatdown.
NO dramatic motive. Just a self important, fed-up, tired old man...losing it. And his bipolar daughter joining in.
Now he's out for himself on the stand. The things he can't remember serve his purpose as well as hers. But he wasnt going to help her out on DV.
He may want her convicted. The State can deal with her then.