HOUSTON  A dog’s sniff helped put Curvis Bickham in jail for eight months. Now that the case against him has been dropped, he wants to tell the world that the investigative technique that justified his arrest smells to high heaven.

The police told Mr. Bickham they had tied him to a triple homicide through a dog-scent lineup, in which dogs choose a suspect’s smell out of a group. The dogs are exposed to the scent from items found at crime scene, and are then walked by a series of containers with samples swabbed from a suspect and from others not involved in the crime. If the dog finds a can with a matching scent, it signals  stiffening, barking or giving some other alert its handler recognizes.

Dogs’ noses have long proved useful to track people, and the police rely on them to detect drugs and explosives, and to find the bodies of victims of crime and disaster. A 2004 report by the F.B.I. states that use of scent dogs, properly conducted, “has become a proven tool that can establish a connection to the crime.”

Scent lineups, however, are different. Critics say that the possibilities of cross-contamination of scent are great, and that the procedures are rarely well controlled. Nonetheless, although some courts have rejected evidence from them, the technique has been used in many states, including Alaska, Florida, New York and Texas, said Lawrence J. Myers, an associate professor of animal behavior at the Auburn University College of Veterinary Medicine.