On April 16, 2003, at 1158 central daylight time, a McDonald Douglas DC-9-82 (MD-82), N452AA, operating as American Airlines Flight 2439 (AAL 2439), was not damaged when it encountered smoke in the cabin while taxiing after landing at the Dallas/Fort Worth International Airport (DFW), Texas. AAL 2439 was being operated by American Airlines, Inc., of Fort Worth, Texas under 14 Code of Federal Regulations Part 121, as a scheduled domestic passenger flight, from Nashville (BNA), Tennessee to DFW. One passenger sustained minor injuries, one passenger sustained a serious injury, 49 passengers and the 5 crewmembers were not injured during the emergency evacuation. AAL 2439 landed at DFW on runway 17L and took the high-speed exit Quebec Seven onto taxiway Echo Romeo. After crossing runway 17C, the airplane turned north onto taxiway Mike, and the first officer started the auxiliary power unit (APU). Shortly thereafter, the #1 flight attendant called the cockpit and reported smoke in the cabin, and "it smelled electrical." The captain shut off the recirculating fan and air conditioning packs, and turned on the ram air. The captain then requested a situation assessment from a deadheading American Airlines captain (Check Airman) who was in first class. The Check Airman reported to the captain that "you've got smoke, and its getting worse." The captain stopped the airplane on taxiway Mike short of taxiway Echo Lima and issued instructions to the flight attendants to evacuate the airplane. The flight attendants evacuated the passengers via the fore and aft service door slides, and forward entry door slide. After completing the ground evacuating checklist, the flight crew exited the airplane. One passenger sustained minor lacerations and scrapes on the right hand, and another passenger sustained a broken right ankle. The passenger with the broken ankle underwent surgery for the injury, and was hospitalized for a period exceeding 48 hours. American Airlines maintenance replaced all slides and a leaking O-ring on the hydraulic transfer pump before returning the aircraft to service. Examination of the aircraft revealed the smoke was caused when the APU ingested hydraulic fluid that leaked from the pump after APU start-up.