I'm always amazed that anybody - much less anybody with a drug stash in their house - would consent to a police officer searching their home without a good reason or a warrant. That said, such methods have stood up in the past as a legal tactic under current 4th Amendment case law (depending on what's said and done at the door). Crooks and non-crooks alike are intimidated by police and most folks don't know their rights in such situations, so often they'll acquiesce. Given how drivers react when police ask to search their vehicles (almost always consenting), there's good reason to believe many would do the same at their residence.
Dallas police began a new initiative today to combat drugs. Citywide, officers are headed to suspected drug houses to "knock and talk" with the occupants.
The technique involves knocking on the door of a suspected drug house and trying to talk the people inside into inviting officers in to search without a warrant. Police can enter without a search warrant if they see illegal activity happening.
Dallas police have long used the technique, but its use will be widened during the next few months to include more officers and more areas within the city. ...
"We're doing this to close these particular locations down," said Deputy Chief Rick Watson at Southwest Patrol, who is heading up the effort.
On the flip side, this is lazy police work that lends itself to abuse when neighbors start calling the cops on one another or officers use the tool perniciously. As I wrote in the comments at the Dallas News Crime Blog, "If these are 'suspected drug houses,' presumably they have reason to suspect them. Why not investigate, establish probable cause and get a search warrant?" Taking morally dubious shortcuts seldom pays off in the long run.
I also suspect, since officers' unstated goal during these visits is to "close these particular locations down," that these targets won't be expressly told they can refuse the search if they choose to do so. That knowledge makes a big difference as to whether people consent, though courts have ruled police don't have to tell them they have that right. In Austin, after APD began requiring informed written consent for searches at traffic stops, the number of vehicle searches performed without probable cause declined 63%.
If Dallas police were serious about ending drug dealing in these neighborhoods, they wouldn't be looking for shortcuts based on rumors but applying strategies with more proven track records. The most successful approach I'm aware of is the High Point model, where police actually investigate, make cases on individuals, then confront them and their families with evidence in an effort to coerce them to change their behavior. Without that community assistance, a new crackhouse pops up as soon as you get rid of the last one. But it's hard work to empower communities to confront crime, while doing "knock and talk" in response to unverified complaints from neighbors basically amounts to engaging in fishing expeditions that require few investigative resources.
The "knock and talk" tactic will inevitably result in arrests here and there, but it won't solve the problem, may create a few, and amounts to taking the easy way out without reducing the city's drug problem.