I read a book, and fascinating it was too, called 'Fatal vision' (from Macbeth: Is this a dagger I see before me?). It was made into a TV movie with Karl Malden and Gary Cole. True story.
A US Marine doctor was living on Fort Bragg with his young wife and two little daughters. One night he phones the MPs in the middle of the night and says the house has been attacked, hes' been injured, he's worried about his wife and children. When the MPs turn up, Mum and the kiddies are dead, and he has a punctured lung.
He says that the littlest one wet the bed, and wanted to sleep in the big bed, so he slept on the couch because he could never sleep with the youngster wriggling all night. Middle of the night, dark, he's woken up by a man standing over him. He struggles to his feet seeing himself surrounded by hippies, including a girl with long blong hair and high boots carrying a candle saying "Groovy! Kill the pigs!" (its 1970, by the way). He can hear his wife screaming as though she's being attacked and the girls are crying. He makes a life-or-death attack on one of the hippies, desperate to reach his family and help them. But he's stabbed in the chest, can't breathe and collapses. When he comes to all is quiet and he makes the call to the MPs. He is able to give them pretty good descriptions of 4 hippies, their hair colour, their facial features, the clothes they were wearing and the badges and patches on them.
All credit to the MPs, within about 48 hours they have decided he did it. Mostly because the only injury he has is a tiny puncture wound between two ribs which unluckily is just deep enough to penetrate the pneuma and collapse the lung. Also, almost nothing in the room is disturbed. Even a precarious stack of magazines on the coffee table hasn't been knocked over. For a marine to be in a life or death struggle in a tiny married-quarters living room and the furniture is exactly where it started, and he has no bruises, no marks on his hands or face, just the tiny wound - what's that about?
And in the bathroom sink, under the mirror, are a few blood splats, quite small, exactly what you might expect to see if, say, a knowledgeable person pushed a scalpel
just far enough between two ribs to puncture his lung.
At first his mother and father in law were incensed with the Army for charging their beloved (US Marine doctor, no less) son in law. But one day the father goes to the house - a sealed crime scene for years) and lies down on the couch. At 3 am in the morning the room is pitch dark. You cannot see
anything, leave alone facial details and hair colour.
Macdonald fought successfully for years, with (admittedly) high class defence teams, even moving to California and becoming a sort of ER doctor to the stars, before finally being convicted. The successful prosecutor kept telling the jury: "If I can prove he
committed this crime, I don't need to prove that he is the sort of person who
might commit this crime."
It is known that Macdonald had been moonlighting in a local ER and was taking diet suppressant pills (=amphetamines) both to keep his weight within Marine regs and to help him stay awake. After many months doing this he was borderline psychotic. The writer, a journalist who had been commissioned to write the
Jeffrey Macdonald is innocent! biography of the court case, theorised that the it was the
older daughter had wet her bed; she wanted to sleep with Mommy, he had an argument with his wife about it, she told him she'd finally had enough and he beat her to death. The older daughter died trying to defend her mother.
Each of the family had a different blood group, so scientists were able to see who had been in which room and generally in what order. As a result, most people were convinced that he killed the youngest daughter, barely more than a toddler, simply to provide the alibi.
So loving fathers, even ones who are so loving that their in-laws think the sun shines out of their a**, can be ruthless killers.
And what is easier than to throw the investigators off the scent by going "Hey! Look! A werido/weirdoes!! He/they must have done it!!! I wouldn't be me, not good old Dad...
(However, check
here for the other point of view...)