Should I open the door if the police knock?
Only if they have a warrant.
If they don’t have a warrant and force their way in, then let a judge sort it out.
If they are in, just remain silent and comply with any command (sit still) .
Do not give them permission to search, even if the situation looks hopeless.
Remember that a lawful search is only admissible if:
a) you give them permission,
b) the police have a warrant,
c) “exigent circumstances” exist.
To preserve the issue for a judge NEVER agree to a search.