State v. Tina M. Miller, 2002 WI App 150, PFR filed 6/3/03
For Miller: Timothy A. Provis
Issue/Holding: Based on evidence that the dog had been trained in drug detection, the police had probable cause to search the automobile once the dog alerted them, including probable cause to search a purse within the car. ¶¶12-15
But, keep in mind this potentially important limitation, State v. Gibson, 141 Idaho 277, 108 P.3d 424 (2005):
Although a drug’s odor detected by a dog alerting on a vehicle provides probable cause to believe that the drug is present and authorizes the search of the vehicle, the mere existence of the drug in an automobile does not of itself authorize the police either to search any other place or provide probable cause to arrest any person in the vicinity. Humphries, 372 F.3d at 659. Probable cause to believe that drugs are located in an automobile may not automatically constitute probable cause to arrest all persons located in the vehicle; some additional factors would generally have to be present, indicating to the officer that those persons possessed the contraband. Id. It has been noted that a dog has the ability to detect very small traces of odors but the existence of a drug’s odor at an intensity detectable by the dog does not definitely establish that the drug itself is present. Matheson v. State, 870 So. 2d 8, 13 (Fla. Dist. Ct. App. 2003). Thus, the dog’s superior ability to detect odors is both a strength and weakness as to establishing probable cause. 3 Id.
 On this point, it is instructive to consider that conditioning and certification programs for drug-detection dogs vary widely in their methods and elements. …