I a cop walks by your open window and smells pot, he can come knocking on your door.
“Gimme a second, I’m just putting on some clothes…”
He can to the same extent that a member of the general public can. A Jehovah’s Witness can walk up to your door; so can a cop. If you don’t want him to, lock your gate.
As lawbuff notes, evidence gained by a random trawl of the yards in a neighborhood is likely to be suppressed. The issue in the case he references in the OP is whether the cops can conduct a sniff of a suspect grow house; in other words, can they bring the dog if they have reasonable suspicion (rather than no grounds at all).
Hey man, he was just walking the dog, you can’t keep them cooped up in the back of a police cruiser all day long.
My $0.02’s worth is that the case will be reversed. The Florida Supreme Court decison is well written, but fails for three reasons. First, the stuff about how the sniff test exposed the defendent to public opprobrium has little basis in the case law for what does and does not contitute a search. Second, there are several Supreme Court cases to the effect that a sniff test isn’t an intrusive search. Admittedly, as the Florida Supreme Court argues, none of these cases involved home searches, but the lack of intrustion is crucial. Because, third, the key Supreme Court case underlying the Florida Supreme Court decision is Kyllo (the infrared scanner case), which states that “the Fourth Amendment draws ‘a firm line at the entrance to the house,’ Payton, 445 U. S., at 590.” ISTM, one’s porch falls on the okay side of this line. From which it follows, if drug sniffs aren’t intrustive, that they don’t need a warrant or probable cause. FWIW, I agree with the Florida Supremes that, if the porch sniff test is a search, probable cause not reasonable suspicion is the appropriate standard. But I think the Supreme Court will rule it’s not a search for purposes of the Fourth Amendment.
I have no idea, legally speaking, as to which way they will rule, but I think its a search and should be disallowed. If they had enough evidence to be randomly walking drug dogs around, then they had enough to get a warrant. If they didn’t have enough to get a warrant, then they have no business using a dog to conduct an external search of the property.
Reconcile with Caballes?
Legally, I don’t think I can correct? If the supreme rules, then that’s the law until we choose to overturn it via legislation. 
However, we are in GD and not GQ; and I side with the dissenters, that a dog sweep is far from infallible, is invasive, and takes up far more time than is reasonable under the circumstances. What I see here, is the police wanting a shortcut alternative to the slow collection of evidence that builds the case for a warrant to be issued. Since the whole point of such a process is to protect the innocent from fishing, bullying, and to reinforce the presumption of innocence, I have an issue with this technique. It is using a tool whose abilities exceed those of a human to search in places where our senses cannot lead us during the course of a properly conducted investigation. That should require a warrant.
OK. I take issue with a couple of your points – how is a dog sniff invasive? And how does it take up any time at all? The Cabelles court said that police could not extend the initial detention in order to accomplish to dog sniff.
While I am uncertain that a sniff is invasive, Caballes does not stand for the proposition that things are invasive only when they waste a suspect’s time. It would undoubtedly be invasive if the police were taking pictures of my wife in the buff through our windows using a telephoto lens, although it wouldn’t actually take up any of her time.
The FL Supreme Court tried to get creative in circumventing clear SCOTUS precedent that a sniff if not a search because the dog can only detect contraband. But I don’t think their creative approach is correct – yes it is invasive of privacy to have cops traipsing about in your driverway and doorstep with dogs, but that’s true whether they have dogs or not.
I think if the factual premise that SCOTUS relies on is true, namely that a dog sniff is essentially just a fairly reliable contraband-detector (since while the dog may learn all kinds of other private information, he can’t tell anyone), then the legal question is just whether you have a right to privacy in contraband. I don’t find that to be an especially interesting or difficult question.
I see the invasiveness of it a little differently - much like adding a GPS tracker, etc - taking a Drug Dog to a person’s house to ‘talk’ at the front door is something that the Police would generally not do - its out of the norm for the police.
If they have enough cause to warrant taking the dog for a walk to the person’s home - then they have enough (or should have enough) to get a Judge to sign off on it.
They (the police) are looking for ways around the system instead of working within it - and this practice must be curtailed at every opportunity.
I should add: It’s a bit of a red herring to talk about how a dog might falsely alert. That’s true, but irrelevant. The question is whether privacy is violated by the fact of the sniff, not whether the sniff is reliable.
The question of the sniff’s reliability is only relevant to what a positive alert should justify. Should it justify immediate entry? Is it sufficient for probable cause? Those are interesting questions, but are separate from the question of whether a sniff is a search.
Well, I feel that the sniff is invasive in the same way using infra-red scanners, or say a hypothetical portable version of that x-ray device at the airport would be. The police should be limited to what evidence they can collect using their own senses at the time. If they are conducting an investigation, then they certainly should be able to provide enough evidence to warrant a pass with k-9. If they can’t provide even this basic level of evidence then they have no reason to have dogs out there in the first place. K-9 are used as support, or in places like ports or air terminals. They are not, (and should not) usually be out on random trawls. That’s fishing in the clearest sense of the word.
Further, upthread we determined that a fenced, gated property was treated differently than one that is unfenced. That is simply absurd. The law should protect all citizens and all property equally, not create classes based on zoning laws or financial ability to construct additional obstacles. I see a great difference in the public at large, and the police while on duty. True, the public can come up to an unfenced door with impunity, but presumably they have business there. The police have no business being on anyone’s private property unless they’ve got some evidence to back up their suspicions, or they are conducting an investigation for the property owner. In the former, they can get a damn warrant. The latter, they were invited.
I think your contention, Acid Lamp, has very little to do with the dogs. If you object to the Police randomly walking up to houses and peering in the windows from the doorstep, then your objection is a much more fundamental one in our country’s Fourth Amendment jurisprudence.
In other words, if the presence of dogs doesn’t make a difference one way or the other about your determination of whether police presence is violating the homeowners privacy, then your’re focusing on an issue that swallows this narrower question.
Speaking of false alerts, the SC also granted Certiorari to another Florida case, to be heard this term, Florida v. Harris.
The question presented is whether a dog “hit” on an automobile is sufficient probable cause to conduct a warrantless search of the car based on the “Automobile exception”.
I find this to be a much more interesting and difficult question, combining a thorny factual question (dog sniff reliability) with an impossible legal question (just how much cause is sufficient for probable cause).
I’d love to see them say that dog sniffs are not per se sufficient for PC, but that instead they need to present the training records to show that this particular dog is a reliable detector (which many departments apparently already do).
Point taken, but the dog is no different than any other invasive tool the police may use when they have reasonable suspicion. At ports and air terminals, for example, the dogs are allowed because contraband is often smuggled in and out at those places. The search is executed fairly and across the board, so the use of the dog is reasonable. They are not violating anybody’s private rights, ( or else they are violating everybody’s which is much the same). OTOH, the use of a dog on a private residence is quite different. In this case the police are using an invasive tool to circumvent their usual process. The process that is designed to keep them in check, and to keep our rights intact. In this case, the violation of the right usually requires a judge to sign off. There is a trail of evidence to support the violation. I have no objection to the use of a sniff dog, only that it be used correctly, and in the proper circumstances.
To be specific, that IS the issue.
Issue: Whether an alert by a well-trained narcotics detection dog certified to detect illegal contraband is insufficient to establish probable cause for the search of a vehicle.
Interesting. Isn’t that question a bit circular? If we assume the dog has been sufficiently-trained to reliably detect contraband, why wouldn’t it be PC? I guess I have to read the briefs. 
I think one of the main differences is that the other invasive tools allow officers to see private things that aren’t contraband. If you use infrared sensors, you can see the lady of the house in the shower. But the dog is a “device” equivalent to a box that just says “Contraband: yes or no?”
ETA: But I totally get what you’re saying. To say that the police are allowed to walk up to a door and knock and ask questions doesn’t negate the intuition that there’s something wrong with them targetting certain homes for this tactic based on something other than reasonable investigative suspicions. But I think capturing that intuition in our existing framework is pretty tough.