Drug Bust on Teen Party

There would be quite of range of responses, depending on a number of factors: what the police are like in this locale, whether it's a small town where everyone knows everyone else or a large city, the neighborhood (or hood), who the parents are (politics matter), whether the kids are known troublemakers or not, whether the kids smart back to the police, etc. Within reason, you can write a scene like this just about any way you want.

I agree with alleycat - there are so many possible aggravating and mitigating circumstances that you could write this any way you wanted, as long as you backed it up.

The police would need to see the drugs or alcohol from the doorway or window. That would give them reasonable cause to enter. From that point, they would try to get someone to claim ownership of the drugs. If no one confesses, the person connected to the house would be charged with possession of any drugs not on someones' person.
Drugs on a person would be tied to that person. Anyone over 21 would be charged with contributing to the delinquency of minors (assuming there are kids <16 years old there). The minors would be written up and MAY be required to appear in family court. if they're between 16 and 21 (in New York) They're considered adults, but too young to drink and the people over 21 would be charged with distribution of alcohol to underage persons. If these (16 - 20 YO) people are not charged with drug possession, they'd be sent on their way. Probably after notifying their parents.

ETA: In many of these cases they are college parties. If no drugs are found, the cops usually just check ID's and toss the underage kids out. If the party is disorderly and a nuisance to the neighborhood, the cops will shut it down, and perhaps arrest the over 21 kids for serving underage persons.

Not that I would know ( ) but they can't come in without permission. They follow those driving off, give giggly sorts outside breath analysis if underage.

Once you drive home safely after they have been following you, they just drive away. Pretty cool.

Now if the homeowner lets them in? I have no clue!

The phone call might change the 'come in without permission' part, mightn't it?

We're all assuming this is happening in the US, so I'll continue with the assumption, but my experience with law is in Canada - I think this rule is the same in both jurisdictions, though.

If the officers have a reasonable believe that a crime is currently being committed (such as illegal drug use), then I'm pretty sure they can come in. Think of it in terms of domestic abuse - the cops can bust a door down to get inside, even if the homeowner (the abuser) tells them not to. I think the question would be whether an anonymous phone call would count as grounds for a reasonable belief. It might be easier for them to observe a few underage drinkers leaving the premises, assume that they'd been drinking inside, and go in to investigate THAT crime.

ETA: But I think backslashbaby's experience is equally valid. The police probably COULD have come in, depending on what they saw, but a lot of police forces don't want the aggravation, and others are genuinely interested in just making sure the kids are safe. This is one of the many factors that were alluded to above - basically, the author can have the cops act any way that works for the plot.

Yeah, I'm not sure any more what counts as probable cause. It has gotten looser in the US since I was at those kinds of parties, but I don't recall the details.

And nowadays, drug dogs are allowed to sniff around anywhere. If they hit, it is probable cause. That's what they do with car searches here -- you have to wait till they bring the dogs if you turned down their request to search.

Just some thoughts for research ideas.