Not sure if this adds anything but here is the excerpt regarding knock n talk (or tap and rap) from my synopsis on the Barry Cooper DVD (volume 2) located here:
https://www.rollitup.org/general-marijuana-growing/58016-never-get-busted-dvd-synopsis.html
Knock & Talk (or Tap & Rap)
It is not illegal for police to knock on your door and begin discussing the possibility of you being involved in criminal activity. Knock & Talks are usually triggered by informants, someone seeking revenge or some other suspicious activity (like a lot of foot traffic going in and out of your house). If you open the door, the police will lie and cheat their way in.
How do you avoid this problem? DO NOT OPEN THE DOOR. Do not go out on the porch and shut the door to talk to the cops. The cops will do anything to get in your house. Just do not open the door. The bottom line is - if the police have a legal right to be in your house, they will NOT be knocking - they will be kicking your door in. Cops also do not care if they trample your rights and lose the case. A drug seizure is a drug seizure and having the case thrown out of court is no problem to a cop. One of my favorite parts of the DVD shows Barry doing what you should do. You hear a knock at the door and upon investigating (looking out the window) you see police. If your door is not locked, lock it. He then yells through a window (or the door) the following: “I don’t open the door for police if you need to talk to me, have your dispatcher call my cell phone or we can shout through the window like this. If you have a search warrant, here are my hands (shows hands) go ahead and kick the door in”.
Bottom line - do not ever, ever, EVER open the door for the police.