A well-trained drug-detection dog should alert to such odors; his response to them might appear a mistake, but in fact is not. See n. 2.
Note 2: ...when a detector dog responds and no drug or explosive is found, do not assume the dog has made an error.
By Culture of TruthFor that reason, evidence of a dog’s satisfactory performance in a certification or training program can itself provide sufficient reason to trust his alert. If a bona fide organization has certified a dog after testing his reliability in a controlled setting, a court can presume (subject to any conflicting evidence offered) that the dog’s alert provides probable cause to search.