It was improper for the government to supply the defense with heavily redacted records concerning a drug-detention dog’s training and performance history. As appellant drove through the primary inspection at the Arizona border, a drug-detection dog exhibited “alert behavior,” and appellant was detained. A human officer then brought the dog to appellant’s vehicle and, directing the dog, had him jump up to the tool box. The dog again alerted and the box was searched. Bundles of marijuana weighing 150 pounds were located inside the locked tool box. Prior to a suppression hearing, appellant was provided a record of the dog’s training and experience in narcotics detection. The records were heavily redacted and appellant objected. The district court ruled that the government satisfied its discovery obligation and denied the suppression motion. Reversed. A defendant must be afforded the opportunity to challenge evidence of a dog’s reliability in a dog-sniff case. The government must disclose the dog’s history, including training records, when a defendant requests this information to pursue a motion to suppress. Here, because the appellate court was not provided with the redacted information, it was unable to assess the dog’s reliability and whether the dog’s behavior provided probable cause to search. The failure to provide the required discovery was not harmless error because the admission of the results of the search affected appellant’s substantial rights at trial.