The police,by their very nature,are nearly always suspicious of people in general,,so it was of no surprise that they'd pointed out how calm Jeremy was when they'd arrived at WHF. Did it not occur to them that Jeremy wouldn't have had the slightest idea as to what may,or may not have happened ? No,,they had him down as the killer.Yeah ! So after slaughtering the family,,and the place looking like a bloodbath inside,,Jeremy is going to be calmly sitting in the car talking to the police ?
What didn't take place in that courtroom was the " psychology " of each individual,,least of all Sheila,,in which to work out who would have been responsible and capable of murder.