In many cases that result in the seizure of drug contraband or currency, a drug dog was used to alert the officer to the presence of possible contraband. The usual defense to such evidence entails an attack on the officer’s probable cause to search, claiming that the dog’s alert does not provide probable cause. The Illinois Supreme Court resolved the issue in Illinois v. Caballes when it ruled that the fourth amendment “does not require a reasonable, articulate suspicion to justify using a dog to sniff a vehicle during a legitimate traffic stop.” However the ruling also specified that the officers follow the accepted procedure of “capture and release,” meaning that officers should conclude the traffic stop, tell the suspect they are free to leave, and then ask the suspect to talk with officers, at which point, search and seizure operations can begin. The article also discusses the claim that contaminated currency can cause a canine to alert; critics contend this claim lacks any scientific validity. Court decisions in relation to this controversy are examined, particularly relating the legality of seizures of currency contaminated with cocaine. Overall, the cases on canine alerts involve decisions based on a totality of circumstances that appear to indicate an acceptance of the substantial probative value of canine alerts. In such cases though, it is imperative that substantial evidence exist to support the Government’s claim.