I'm not an attorney, but here, in Illinois, I believe there is some sort of charge which can be brought against spouses who stand by and allow their kids to be "abused" (and we all probably agree that what Andrea Yates did would be the final, worst case of abuse) and don't show that they did EVERYTHING humanly possible to stop it. Kind of like the Mom who gets liquored up and piles the kids in the car to go to MacDonald's and ends up wrapping the car around a tree. If the Dad does anything short of laying under the car wheels, he could be held criminally liable. And even then they would say "he should have called the cops IMMEDIATELY and reported the Mom as intoxicated, given a vehicle description so she could have been stopped!"
If a court can prove that the other spouse was negligent, in this regard, I think the other spouse can face prison time, also. Kind of like "it takes two to tango". Like I said, I'm not an attorney, maybe someone more educated about this will give us a clue.