When detectives have to resort to triangulating your cell phone's location during the time of what is being investigated as a vicious murder, because they have no eyewitnesses as to your location and alibi, and no footage of you on hospital security tapes, you are a suspect. Max didn't have to be dead for revenge to be a motive for hurting Rebecca. He was mortally wounded, and not expected to live at that point. (Ann Rule makes this clear, as well.)
LE didn't triangulate the cell phone of the dog kennel owner, nor investigate his whereabouts during the time of Rebecca's death. He was never a suspect.
BBM. With all due respect, Ann Rule's book says that there were witnesses to Dina's location.
The cell phone records were done weeks after RZ's death. To me, it seems detectives only resorted to the cell phone triangulation to appease those who accused Dina of being involved. And, despite the eyewitnesses to Dina being at the hospital AND the Sheriff announcing the cell phone triangulation confirmed Dina was at the hospital, some of you continue to accuse her of murder.
At the time of RZ's death, the hospital had requested a CPS investigation because of discrepancies in descriptions of the "accident" vs Max's visible injuries...descriptions that came from RZ.
Being the subject of a child abuse investigation is far more a motive for suicide than it is a motive of murder by the mother of a child she believed was injured in an accident. Cops hadn't told Dina of the child abuse investigation at that point.
JMO