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...
And many innocent people have been killed by policemen in no-knock raids.
Police can at least take appropriate precautions, such as wearing bullet-proof vests, while innocent civilians sitting at home unaware of any danger cannot take any such precautions once the police come busting through the door.