On July 25, 2002, about 1600 mountain standard time, a Cessna 172P, N97056, collided with a standing Cessna 152, N152BR, while taxiing for departure at Falcon Field Airport (FFZ), Mesa, Arizona. Sawyer Aviation Training Center owned and operated both airplanes under the provisions of 14 CFR Part 91. The Cessna 172P received minor damage and the Cessna 152 received substantial damage. Neither the certified flight instructor (CFI) in N97056, nor the student pilot in N152BR was injured. The positioning flight was intending to depart FFZ, with a planned destination of Scottsdale Airport (SDL), Scottsdale, Arizona. Visual meteorological conditions prevailed and a flight plan had not been filed. In a written statement, the CFI, who was piloting the Cessna 172, reported he was attempting to taxi to the run up area for runway 22L. His student was taxiing in the Cessna 152 directly ahead of him, and he was planning to fly behind her en route to SDL. Before taxiing, he completed a preflight inspection and a brake check, both of which showed no abnormalities with the airplane. While taxiing, he had to complete a sharp right turn, which he accomplished by added right brake pressure. He continued taxiing at 1,000 rotations per minute (rpm), which was about 13 miles per hour (mph). Just before approaching the run up area, he began to reduce the throttle and applied brake pressure. The right brake did not respond. In an effort to avoid a propeller strike, the CFI decided to remain on the taxiway. He applied full left brake pressure and the airplane's left wing tip collided with the Cessna 152's vertical stabilizer. The airplane continued to the left and departed the taxiway. During the accident, the Cessna 152 incurred damage to the vertical stabilizer and rudder. During a telephone interview with the National Transportation Safety Board investigator-in-charge (IIC), the operator of both airplanes thought that the CFI was probably taxiing too close behind the student pilot. When the student pilot turned and stopped, the CFI did not have enough time to react and collided with the airplane. The operator stated he talked to a controller in the tower that witnessed the accident. The controller indicated that the airplanes were taxiing within a very close proximity of one another. The operator also stated that Royal Aviation recovered the plane shortly after the accident had occurred. While towing it down the taxiway, they tested the brakes. Both brakes appeared to be functioning properly. He later talked to Arizona Aviation, a repair shop that was assessing the damage. They stated that after a thorough inspection they could not find any malfunction of the braking system. No repairs were made on the braking system.