A recent decision from the Court of Appeals of the State of New Mexico makes it clear that a protective sweep of the inside of a Defendants' residence, incident to an arrest taking place outside of the residence, is impermissible unless there is a "reasonable belief based on specific and articulable facts that the area to be swept harbor[s]an individual posing a danger to those on the arrest scene."
The facts as stated by the Court in State of New Mexico v. Eckard are pretty straightforward.
Felony warrants were issued for the Defendant and his wife. Several agents arrived at the house to serve the warrants. Some of the agents went to the front door while some of the agents went around to the back of the house. There was no response to the agents' knock on the front door of the house. The agents that went around to the back of the house found the Defendant and his wife sitting at a table about ten feet from an open sliding door.