On August 18, 1999, at 1420 hours Pacific daylight time, a Diamond Katana DA 20-A1, N854DF, sustained substantial damage during an off-airport landing following takeoff from the San Carlos, California, airport. The off-airport landing was precipitated by the canopy opening during the takeoff initial climb. The certificated private pilot received minor injuries. The aircraft was operated by Diamond Aviation under the provisions of 14 CFR Part 91, and was rented by the pilot for a local area personal flight. The flight originated from the San Carlos airport at 1419. Visual meteorological conditions prevailed at the time and no flight plan was filed. On takeoff, at about 200 feet agl, the left canopy latch popped open. The pilot looked at the right canopy latch to verify that it was latched and saw that it was. He began an early crosswind turn and radioed the tower controller that he was going to return to the airport due to problems with the canopy. As he leveled the wings after the crosswind turn, the canopy opened into the airflow. He held the control stick full forward and made a "mayday" call. The pilot made a nose low, forced landing at about 60 knots on a dirt road about 0.75 miles off the departure end of runway 30. The pilot was transported to a hospital, complaining of back pain. A Federal Aviation Administration inspector examined the aircraft's canopy after the accident. He stated that he could not identify any malfunctions with either of the canopy latches. He then functionally checked both of the corresponding micro switches, which sense latch closure by physical contact. If either switch opens, the cockpit canopy open enunciator light will illuminate. Both micro switches and the enunciator warning light were found to work properly. According to engineering personnel from Diamond Aircraft, if the aft hinged canopy opens in flight, a significant increase in drag occurs and controllability becomes marginal.