Because so many of you have mentioned MacDonald, last night I got the audiobook, (Fatal Vision.) Something interesting occurred right at part 1 ch6. The military had not asked much of MacDonald, re his version. For 6 weeks they had been gathering evidence and were on to him. So they invited him in for his first interview, and after Mirandizing him, he says, nah, I don't need an attorney. So he blabs on for about 3-4 hours, contradicting himself, shooting out lead after lead for them to follow. Before this interview he either forgot, or didn't know that each person in his family had a different blood type, A AB B & O. So, it was like breadcrumbs for LE, they could follow the blood all over the house.
But here is how it relates to the Watts case, IMO. The interviews with CW were similar to the cocky attitude that Macdonald showed for so many hours. Guys that are so self deluding that they think they can bluff their way through life.
MacDonald had 2 daughters just a little bit older than the Watts kids. In the interview it was so telling, one just wouldn't quit wetting her bed, but she often got in bed with Mom and Dad and did the wetting there. Which could have been the trigger that night. He goes to bed with his now chubby 5 month pregnant wife, finds his side of the bed wet, and OMG. Also, in the interview he refers to one of them very very passive and girlish, and he says LIKE COLLETE. The other one tomboyish and take control kid. Paraphrased.
Remember when CW was critiquing the girls in his post murder interview, wouldn't eat right, whatever.
No psychologist here, but reading the MacDonald interview, pre-lawyering up, reminded so much of CW interview.