Dahle is charged with possession of heroin. Prosecution witness Walker, an experienced dog trainer, testified that he was in the airport with a dog trained to detect heroin. As Dahle with a dog trained to detect heroin. As Dahle approached, the dog immediately became alert and pawed and barked frantically at Dahle's briefcase. Dahle managed to run outside and throw his briefcase into the river, from which it could not be recovered. After Walker's experience is established, he is asked to testify as an expert that the dog's reaction told him that Dahle's briefcase contained heroin. Walker's testimony is 
admissible, as evidence of Dahle's guilt.  admissible, because an expert may rely on hearsay.  inadmissible, because it is based on hearsay not within any exception.  inadmissible, because of the unreliability of the reactions of an animal. 