Watching the series I felt it was really odd. The family behaved oddly. Laughing and joking throughout his bail and trial, just some of their characteristics etc.. but I didn't think there was enough shown from what we saw to convict him.
I read a lot last night when I finished the series - the owl theory, how the son was a bit of a dangerous guy - in and out of prison (once for planting a pipe bomb), how Michael was in a lot of debt, how Kathleen was supposedly dead for 2+ hours etc... And now it makes me question if he was involved. I read a lot but don't know where this stuff has come from or how true it is but if true, I would quite like to know how the defence could explain it away. Even the spatter on the inside of his shorts - how are they explaining that? Was he really outside for 2+ hours whilst she lay dead? In December?
And in the last episode, it was revealed that the Police knew the blowpoke was in the garage - they had removed it from the scene, took pictures etc... Why? Why put it back? What advantage is it for them to leave it there and hope that the family find it, which they would most likely do given it's location? That was all odd. And explains how the family missed it at first.
EDIT: Has there ever been a DNA test on his two daughters...? The non-biological daughters? One looks really like him.