“Undercover HPD claims to have bought heroin at the house.”
Then why not arrest them on the spot at the time of the crime?
L
Because usually a controlled buy is done by a CI who is working off a case of their own. Cops don't want to give up their snitches. If the undercover cop did the buy they usually wait until they've bought as much from as many as the can before they serve the warrants because once the first arrest goes down everyone now knows that guy is a cop.
It’s called “building a case”.