How about this strategy? Cop goes up to door, knocks, and asks to speak to occupant. If occupant is willing to talk, cop tells occupant about nearby crimes in the neighborhood, gives his card, and asks occupant to call if he sees anything. If occupant is unwilling to talk at the time, cop says, "No problem--I'll come back later". If there's a drug dealer inside who flushes all his drugs, well the cop just destroyed thousands of dollars worth of drugs without endangering anyone. Plus if the cop repeats this gambit one or two more times, any drug dealer is going to be loath to destroy his inventory over a false alarm. So at that point, the cop can serve a search warrant having thoroughly established his bonafides and convinced the crooks not to flush the evidence.
Or shut off the sewer:')
Point taken. I'm getting from the article that the cops had already made a purchase from this house and although they inconsiderately broke the door down, the woman started firing first.
How about this strategy? Cop goes up to door, knocks, and asks to speak to occupant. <<<<<<<<<<
Many an officer has been killed on the job serving warrants before they ever got to the door. And often, the worst threat isn't even the person you're serving, it can be the nutcase next door who has a warrant out for his arrest and thinks you're coming to get him when you walk up the driveway or approach the house next door.
There are many, many times when ruses are used to gather information, but if "Sam" was known to be armed/dangerous/hinky to begin with, they may have decided to get in as quickly as possible, which is often the safest for all concerned before anyone inside starts anything stupid.
Obviously, the key is to be extraordinarily careful in gathering intel and putting the operation together so that nobody ends up hurt, which is overwhelmingly how it usually turns out. The tragic endings are not always the fault of the officers...