The pilot stated that during the takeoff roll he had right rudder input applied to counter the left turning tendency and upon achieving 45 miles-per-hour, the airplane "...violently pulled hard left and exited the runway onto the grass field then proceeded to come to rest in a ditch adjacent to the runway." Examination of the runway by the FAA inspector-in-charge revealed tire marks associated with "...tire skidding..." from both main landing gear tires beginning approximately 700 feet down the runway. The mark from the left main landing gear tire showed evidence of "'...chirping or skipping' due to heavy braking (locked up)..." for approximately 75 feet before becoming a continuous black mark in length. The mark from the right main landing gear also indicates evidence of heavy braking but did not leave any indication of being locked up. The marks on the runway from the landing gear tires veered to the left and the mark from the left main landing gear stops approximately 30 feet before the edge of the runway, while the mark from the right main landing gear tire continued showing signs of heavy braking. Impact damage to the 1,000 foot remaining sign was noted, and the airplane traveled off the runway onto grass, and collided with a ditch. Postaccident operational testing of the left brake assembly revealed no discrepancies. No brake drag was noted upon release of the left brake. The left main landing gear tire appeared new, and there was no scrapes or scuff marks on the tire. Inspection of the left brake rotor revealed no evidence of warping, and the brake pads appeared new.