On March 13, 2012, at 0950 mountain standard time, an experimental Cook Smith Aviation Replica SU, N712AZ, veered from the runway during landing at St. Johns Municipal Airport, St. Johns, Arizona. The private pilot sustained minor injuries and the certified flight instructor (CFI) was not injured. The airplane was substantially damaged. The pilot was operating the airplane under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed. According to the pilot, he purchased the airplane on March 12, and was ferrying it from Arizona to Texas. The CFI was providing flight instruction to the owner during the flight. While landing for fuel at St. Johns on March 12, the pilot discovered that the left brake was less responsive than the right. The airplane veered off of the runway, but incurred no damage. The pilot indicated that the brakes were not operating on either the right or left side. The pilot and CFI then decided to bleed the brake lines. The brakes were successfully tested during taxi tests, followed by touch-and-go takeoffs and landings, and the pilot and CFI remained overnight in St. Johns. The following morning, the brakes were tested again, and found to be operational. The winds were calm. The pilot and CFI departed to practice touch-and-go takeoffs and landings. During the fourth landing, the left brake was not as responsive as the right brake. The pilot reported that the right brake locked up and the airplane swerved to the right, skidding off of the runway, and the airplane came to rest inverted. The certified flight instructor (CFI) was interviewed following the accident. He reported that he was flying with the aircraft owner from Arizona to Texas. They had landed at St. Johns the previous day and encountered a problem with the brakes in the airplane. The airplane departed the runway surface but resulted in no damage. They elected to bleed the brake system and completed post maintenance checks on the airplane. No problems were noted. The following morning they completed three landings successfully. On the fourth landing, the brakes locked up and the airplane veered off into a gully. The CFI was not on the flight controls at the time, but indicated that the left brake failed. The CFI stated that the pilot had about 10 hours in a similar make and model airplane as the accident airplane. He gave the pilot his tailwheel endorsement the morning of the accident; however the CFI did not hold a current airman medical. 14 CFR Part 61.31 states, in part, "...no person may act as pilot in command of a tailwheel airplane unless that person has received and logged flight training from an authorized instructor in a tailwheel airplane and received an endorsement in the person's logbook from an authorized instructor who found the person proficient in the operation of a tailwheel airplane." The FAA accident coordinator examined the airplane following the accident. No mechanical anomalies were identified with the braking system.