There's no way Oliver would've gotten away with all three of those killings had authorities simply carried out death investigations. Especially the mom's death. What was she even doing at home and under Oliver's care whilst hooked up to all of that ICU equipment anyway?? She'd have been in the hospital!
Because the movie made no sense. From the beer/bike plans that worked perfectly to picking the rocks with names in the water. Nothing made fucking sense in this BS movie.
I'm pretty sure those life support machines keep a record of everything and "tattle" if anything goes awry. Anyone checking the diagnostics should see it was tampered with and/or experienced sudden suspicious behavior. Not to mention, Oliver would've had to put the tubing back into her airway the exact same way it was before and that's highly unlikely given he had no medical training and had RIPPED that thing right out of her along with all of its peripherals.
Oliver knew and did a lot of things that he probably shouldn’t have…he could have spent time learning how to place that equipment correctly…he was an Oxford guy or something after all…
And there would always be the suggestion that she pulled it out herself in some kind of fit and he just wasn’t around to do anything about it.
I can see hi getting away with Felix and his sister. His autopsy would have shown copiuos amounts of drugs in the system with plenty of witnesses to corraborate that in the party. And sister being distraught over his death would also be a viable explanation. The mothers death though was certainly writers just giving up.