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I'm sorry to hear about your situation. There's no requirement that the dogs be walked around the vehicle a number of times, or even once. They can be led to a specific spot, and if they indicate presence of drugs (or trace amounts of it, assuming that the trace amounts were there) then that would be enough. So the fact that the dog was not walked around is not, in and of itself, enough to get the case dismissed. Rather, it would need to be argued that the failure to do so somehow "taints" the evidence. And the dog barking might not be enough either. Now taken together (for example, if you appeared to be intoxicated, or they "smelled" marijuana, etc...) then that could be enough for probable cause. But a bark alone could, potentially, be excluded from evidence, and the search could be thrown out due to a lack of probable cause.
False alerts are more common than is thought. Think about it: if the dog barks and no drugs are found, the person doesn't get charged with drugs, and the validity of the bark is not challenged. The only time it goes to court is when there are drugs. So from the court's perspective (the cases that they see), 100% of the cases where the dog barks, drugs are found. They never see the cases where drugs are not found after a bark. The point is that the evidence could be challenged (potentially) if there was no other evidence found or observed prior to the bark.
That being said, you need to contact an attorney in your area that deals with drug cases. Go to www.lawyers.com or www.legalmatch.com to find an attorney in your area. You should be able to find one that will give you a free initial consultation and better advise you of your rights, any problems with your case, likelihood of success, how courts are treating cases such as yours in your area, and what you should do next.
Hope that clears things up a bit. If you have any other questions, please let me know. If not, and you have not yet, please rate my answer AND press the "submit" button, if applicable.
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Thank you, ***** ***** luck to you!