Ah sorry for not being clearer. The "fault" is not liability or similar but social falt; complicity. The casual or formal arrangement with the police allowed the persecution of this nurse.

Yes cops are often allowed in (elsewhere I list off some of the various situations I've seen for allowing police non-warranted entry in these sorts of arrangements) but it's almost never blanket permission, as that leaves the hospital legally open for all kinds of tedious lawyer shit (lots and lots of hippa mostly) and the more permissive agreements generally still have stipulations about medical staff assent. However they are still required to have a warrant if that permission agreement isn't in place to access any non-public ("anywhere you'd need a vistor badge for" is a helpful way to think of it, even if the badge itself isn't required. The definition of what is considered public/private is quite fascinating if you're a huge boring asshole (like me) - for example in some jurisdictions, separate warrants are required to access the private hospital areas and patient treatment areas / rooms.

(Sorry for the nerd ramble, I was recently on a project collecting and collating these agreements so I have Read. So. Many.)