Whether anyone believes he's guilty or not, the defense definitely presented a case that had more than enough reasonable doubt to find him not guilty. That is all ANY defense has to do. There was so much that came out after the fact of how much corrupt and false testimony there was on the prosecution's part that he should have been found not guilty from the start. The judge even says later there were things that shouldn't have been allowed into evidence in the first case.
Throughout the whole series, I believed that it was more than a fall but not a beating that happened, some sort of freak accident that no one would would come up with unless they actually witnessed it. Truth is stranger than fiction sometimes. When I saw the owl theory at the end and found out about the hairs in Kathleen's hands with microscopic feathers it totally backed up what I thought about a freak accident. As for their marriage, there are many marriages, especially second marriages and of people in that general age range, that are based on a friendship and companionship.