This is in regard to this news story:
http://www.theneworleanschannel.com/...83/detail.html
I came up with theory years ago after watching many Dracula movies as a kid.
You should view all police as Vampires.
If you recall in the old movies and some of the new ones, Dracula could never enter your house unless you invited him in.
Same way with police officers. This is why they always ask if they can come in when there is trouble nearby.
This allows them to do a cursory search. Once something that is in plain view that is clearly against the law or signs of something amiss are spotted then the search can and will expand.
However the tricky part is the rules of the invite.
If someone calls 911 to report an incident within the home then you've pretty much invited them.
If it's just your neighbor calling to complain about noise, barking dog etc they have no reason to be in your house, but they will want to come in so they can see if you've left your crack pipe or bong laying about.
If they ask to come in, tell them no and continue talking to them at the door or step outside and shut the door behind you.
If you rent your landlord cannot give consent to search.
However if you're away for a day or two and someone calls your landlord to report water flowing out of your house and he comes in and during an emergency repair discovers your meth lab you're fucked.
Your roommate cannot give consent to search private areas.
He may give the police consent to search the living room, kitchen, all public areas etc but your bedroom is pretty much off limits.
My suggestion take it a step further and go out and get a doorknob with a lock and key, this will further prove that your roommate did not have general access to your private areas and therefore cannot give consent.
Anyway I am not a lawyer and of course none of this is going to be 100% applicable to every situation or state law.
But these are general things you should consider when dealing with local law enforcement.