On February 8, 2002, at 1126 mountain standard time, N434QS, a Gulfstream Aerospace G-IV, operated by Executive Jet International of Bluffton, South Carolina, was not damaged when it encountered turbulence while descending en route to BJC, Jefferson County Airport (Jeffco), Broomfield, Colorado. There were no injuries to the airline transport captain and first officer and one passenger, but the flight attendant did sustain a serious injury. Visual meteorological conditions prevailed, and an IFR flight plan had been filed for the corporate flight being conducted under Title 14 CFR Part 91. The flight originated at San Jose, California, at 0825 Pacific standard time. According to Federal Aviation Administration documents, the Denver Air Route Traffic Control Center (ARTCC) advised the flight crew of possible severe turbulence over TOMSN intersection at Flight Level (FL) 190 (TOMSN intersection is located approximately 31 nautical miles north-northwest of Jeffco Airport). According to the captain's written statement, as the airplane descended on the TOMSN 3 STAR (Standard Terminal Arrival Route), she checked BJC's ATIS (Automated Terminal Information Service) that advised of moderate turbulence below 10,000 feet msl. She briefed the flight attendant that turbulence was possible at lower altitudes, and that he should be seated and restrained if the "Fasten Seatbelt/No Smoking" sign was to illuminate. As the airplane vacated FL 250, ARTCC advised the crew of possible severe turbulence over TOMSN intersection and to stop its descent at FL 210. The captain turned on the "Fasten Seatbelt/No Smoking" sign. Shortly thereafter, as the airplane passed FL 220, the airplane encountered "severe turbulence" that lasted until the airplane reached about 3,000 feet (above ground level). She heard the flight attendant screaming, but was unable to check him because of more demanding flight duties. The pilot asked ARTCC for priority handling to the airport, and to have emergency equipment standing by. The flight attendant was taken to a local hospital where X-rays revealed he had fractured a bone in his ankle. The flight attendant later told the captain that prior to encountering the turbulence, he had left his seat to retrieve a lint brush from the galley for the passenger. He heard the "Fasten Seatbelt/No Smoking" chime and returned to his seat. The airplane encountered the turbulence before he could fasten his seatbelt and he was thrown about, landing on his ankle.