LE needs a legal reason to enter, if that was not followed, they entered "illegally". Put that aside... if anyone entered that house and is not the killer, then they entered a crime scene. I''m sure a good lawyer would make mincemeat of a case/evidence if a scene was tampered with or perceived to be tampered with etc etc. A thorough wellness check if given permission to do so, would include the whole house and exterior. A lazy LE might have cut corners and not done a thorough check, missing one of the biggest crime scenes (or at least most famous) in Canada = mud on face big time. Ah heck, maybe it was a busy night and there was something more pressing than an alarm that possibly kept going off all week. I'm sure alarm calls are a dime a dozen, and if a home owner wants a key holder to attend, then they need to pay for this service with a company who provides it, and not expect LE to provide (big difference between a wellness check and an alarm)
Sigh... my cameras work fantastically, my alarm eats 1 bowl of kibble per day, and poops.....