Yes he would cover for her...stay married to her til the end...they had many secrets....who else is going to raise Burke?.....and she probably did go psycho again.....it just didn't lead to another murder.
UK....
You can turn this around and ask the same thing. If Burke killed her, he's crazy and needs help. Would they want a child who bashes heads in during snacks in their house? Imagine family meals for starters. YOu would be able to cut the tension with a knife. Also imagine the two of them going to bed every night knowing they have to sleep while the lunatic could come in there at any time and do to them what he did to her.
What are these many secrets you reference?
Burke could have been raised by relatives or by John with the help of a boarding school. He could have afforded the best. If you believe Patsy did all of those horrific things to his little girl, wouldn't John, with all the time he spent at work, be naturally concerned for his son? But it doesn't appear he was concerned in the slightest.
I don't think you can turn it around without making a false equivelency argument as Burke was not a grown-*advertiser censored* adult who did these things to his own child. His parents may have convinced themselves it was an accident, especially if they did most of the staging. Just an excitable boy who lost his temper and hurt his much smaller sister without really understanding the consequences of his actions. And we have no idea what kind of therapy Burke received after the murder. For all anyone knows he got extensive help.