I believe he's guilty. His family was horribly overkilled and yet he ends up with a bruise/bump on his forehead, some scratches and a clean incision to his left chest area? He was the biggest threat in the house; why bash in a 5-year-old's skull and give the male Green Beret a tap?
If we're to believe his version, four hippie intruders, high on LSD, entered the MacDonald home on a rainy February evening through a back door. They walked through the master bedroom without awakening Colette. They walked down the narrow hallway without awakening Kimberley or Kristen. They walked by MacDonald sleeping on the couch in the living room and into the kitchen, where they opened drawers until they found a knife and an icepick. They then walked back by MacDonald, to start their attack on the family in the bedrooms -- neither time awakening him.
Colette and Kimberley were bludgeoned with a wooden slate that came from the master bed, so at some point that was obtained from the master bedroom.
The intruders apparently decided to obliterate this family but did not bring their own weapons. And they managed to leave not a single footprint or mud/dirt from outside. MacDonald's wallet was sitting out in the living room (later stolen by an ambulance driver) and Colette's handbag was on the dining room table. Neither were touched by the alleged intruders.
MacDonald says he attempted resuscitation on his family members. Both little girls were found on their sides on in their beds -- not on their backs and on the floor. MacDonald, as a doctor, would know they would need to be on their backs and on a hard surface. Neither bedroom light had been turned on; MacDonald apparently tried to render aid in the dark. Both Colette and Kimberley had horrific head injuries, resulting in blood on their faces. But no blood was found around MacDonald's mouth.
During the so-called attack in the living room, MacDonald claimed to have been struck by what he said he thought was a baseball bat and saw "the glint of a blade" before feeling what he assumed was a punch but later came to believe was a stab wound. While giving an interview in the hospital, when he got to this portion of his story, he said "that is when I must have gotten stabbed with the icepick."
How did MacDonald know an icepick was involved? All three weapons had been found under a bush outside the back door. MacDonald claimed he never went out the back door. He claimed he never saw his wife or daughters being attacked. He claimed he saw the glint of a "blade." Icepicks don't have blades. He denies turning on any lights to treat his family. So how does he know an icepick was used in the murders? And why would four fleeing killers stop to place the weapons under a bush?
These things can't be explained away and they point at MacDonald and only MacDonald.