Prior to 2006, if the police raided your home they had to prove that the raid was executed in the proper manner. If it wasn't, then the evidence they found might not be admissible in court.
In 2006, the United States Supreme Court issued Hudson v. Michigan. In that case, a regular search warrant for Hudson's home was executed as 'no-knock" warrant. The question for the court was whether the police could still use what they found, even though they did not execute the warrant properly. The Supreme Court ruled that they could.
After that opinion, I wondered why any police force anywhere would bother knocking ever again. There's no benefit to police by knocking, and now the Supreme Court has said that even if the police do not knock, they still get to use what they find to convict the homeowner.
Since Hudson, it seems like we have seen a rash of botched no-knock raids that have resulted in innocent people getting shot and/or disfigured. I wonder whether the Supreme Court opened the door to this or whether other forces were at play. Or both.
And no discussion of no-knock raids would be complete without Lindy's somber "No Knock Raid."