On August 25, 2005, at 1430 Pacific daylight time, a Piper PA-28-236, N4366K, was substantially damaged when it impacted trees after veering off runway 14 at the South County Airport, San Martin, California. The airplane was registered to and operated by the pilot under the auspices of 14 CFR Part 91 as a personal flight. The private pilot and his passenger were not injured. Visual meteorological conditions prevailed for the cross-country flight that originated from Palm Springs, California, at 1200. During a telephone interview with the National Transportation Safety Board investigator, the pilot said the flight and landing on runway 14 (3,100 feet long and 75 feet wide) were uneventful. The airplane was rolling down the runway around 15-20 knots when he applied brakes to slow down. The airplane then veered to the left, exiting the runway surface, and impacting trees. The pilot believed the right brake failed. According to the pilot's written statement, he attempted to stop the airplane during the landing roll out to exit on the first taxiway; however, when he applied the brakes he felt no brake pressure on the right side. As the airplane veered to the left, he applied right rudder pressure and power to abort the landing. The airplane proceeded down the runway; however, the pilot reduced the power to idle, as there was not a lot of remaining runway. The pilot again touched the brakes and the airplane veered left off the runway. The nose landing gear was collapsed aft, the wing tip fairings were broken off, the left wing was pushed aft, and the engine firewall was crumpled. According to the Federal Aviation Administration inspector who responded to the accident site, he and a mechanic tested the brake system. According to the inspector the brakes had equal pressure, but were both spongy, and when depressed, went to their stops. No leaks were noted in the brake system. According to the pilot, the last annual inspection took place in May 2005, and no anomalies with the airplane were noted since the annual.