On June 18, 2003, about 1456 eastern daylight time, an Embraer EMB-145LR, N294SK, registered to Wells Fargo Bank Northwest NA, operated by Chautauqua Airlines, dba Delta Connection as flight 6355, from Indianapolis, Indiana, to Orlando, Florida, encountered turbulence while descending over Taylor, Florida. Instrument meteorological conditions (IMC) prevailed in the area at the altitude flown and an instrument flight rules flight plan was filed for the 14 CFR Part 121 scheduled, domestic, passenger flight. The airplane was not damaged and there were no reported injuries to the airline transport-rated captain, commercial-rated first officer, 49 passengers, or one flight attendant. One passenger sustained serious injuries. The flight originated at 1222, from the Indianapolis International Airport, Indianapolis, Indiana. The captain reported that when the flight was 35-40 minutes from landing, the flight progressed into a very fine layer of cirrus type clouds resulting in being in IMC with occasional light turbulence. He switched the seatbelt sign on that had been off, and advised the flight attendant of the potential for adverse weather for the destination area. At the same time, air traffic control (ATC) advised the flightcrew of amending their arrival to the destination airport. The ride conditions was requested from the controller who informed the flightcrew that an occasional light chop had been encountered at all altitudes, but no moderate turbulence had been reported. The captain continued advising the flight attendant via crew interphone, and about 2 minutes after the seat belt sign had been illuminated, the flight encountered moderate turbulence which lasted approximately 15-20 seconds and was not depicted on the weather radar display. The flight attendant hung up the interphone to check on the passengers, while the first officer advised ATC of the encounter. Approximately 3 minutes after the weather encounter, the flight attendant advised him that a passenger had been hurt. A medical emergency was declared and the flight proceeded to Orlando where an uneventful landing occurred. The flight attendant stated that during level cruise flight with the seatbelt sign off, the passenger who would become injured and her daughter got up to use the lavatory. The seatbelt sign then came on and the captain advised her on the interphone about the landing and the fact that the airplane was being rerouted. The seatbelt sign had been on for at least 2 minutes when the flight encountered turbulence. She hung up the phone and sat down until it was safe to get up then went to assess the situation. She and the passenger's daughter tried to get the lavatory door open and she then advised the captain of the situation. The lavatory door was then opened and another passenger assisted the injured passenger to seat 18B. She noted the passenger had an injured foot and made an announcement whether there was any medically trained person on board. An on-board emergency medical technician (EMT) and a fireman helped stabilize the injured passenger's foot. The cabin was prepared for landing and after arriving at the gate, the passengers deplaned, and EMT's assisted the injured passenger. According to ATC information, the flightcrew was in contact with the Jacksonville Air Route Traffic Control Center and at 1454:19, a flightcrew member advised the controller that the flight was level at flight level (FL) 280. At 1454:45, the controller cleared the flight to descend to FL 270, and at 1455:51, cleared the flight to descend to FL 240. At 1456:05, a flightcrew member advised the controller that a passenger had fallen due to turbulence, and at 1456:38, a flightcrew member advised the controller that a passenger had a broken foot, and declared a medical emergency. Radar data indicates that about the time of the accident, the airplane was at 27, 400 feet mean sea level.