On August 12, 1999, at 1234 mountain daylight time, a Coleman Lancair IV P homebuilt, N124KM, was substantially damaged when it collided with terrain during landing roll at Aspen-Pitkin County/Sardy Field, Aspen, Colorado. The private pilot and one passenger were not injured. The personal cross-county flight was being conducted under Title 14 CFR Part 91. No flight plan had been filed for the flight which originated from Goodland, Kansas, at 1145 central daylight time. Visual meteorological conditions prevailed. According to several FAA Air Traffic Control (ATC) personnel, during the pilot's first attempt to land on runway 15 at Aspen, the aircraft's altitude was too high to successfully land. The pilot advised the tower that he needed to perform a go around to lose more altitude. During his second landing attempt, one controller noted the aircraft's ground speed to be 270 knots while on a 3 mile final. Several controllers observed N124KM touch down near taxiway A2 (see enclosed personnel statements), located approximately 1,800 feet from the beginning of the 7,004 foot runway, and then noticed that the aircraft failed to stop. They witnessed the airplane depart the end of the runway slightly left of the centerline into a grassy field. According to the pilot, he touched down at an indicated airspeed of 95 to 100 knots (normal landing speed for the Lancair IV P) and the wind at the time he landed was from 300 degrees at 10 knots. He rolled out with the nose up to bleed off airspeed. After letting the nose settle onto the runway, he applied brake pressure and noted that the right brake appeared "soft." He pumped the brake, but was unsuccessful in restoring pressure. He stated that he was not able to initiate a go-around due to the high density altitude (calculated to be 9,828 feet above mean sea level), and the limited remaining runway that was available. The airplane departed the runway overrun and went into a grassy ditch surrounded by rocks. The aircraft sustained damage to both wings, the nose wheel, and propeller. According to a mechanic employed with Aspen Base Operations, the local Fixed Base Operator at the airport, when he went to remove the aircraft from the field, he observed a red fluid running down the right gear strut attached to the fuselage. At this investigator's request, a second mechanic was asked to perform a functional brake test of the right brake. According to the second mechanic, the left pedal was "firm," and the right brake was "soft = no brake" (see enclosed statement). According to an FAA ATC manager employed at the Aspen airport, the primary landing runway used at Aspen is 15, despite existing wind conditions. This is primarily due to mountainous terrain conditions surrounding the airport and the sloping runway gradient.