On June 27, 2019, about 1500 central daylight time, a Cessna 525, N318RW, sustained minor damage when it was involved in an accident near Janesville, Wisconsin. One passenger sustained serious injuries, the pilot sustained minor injuries, and two passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 business flight. The pilot had anticipated some turbulence along the route of flight, briefed the three passengers, and had the seat belt sign turned on. At flight level (FL) 240, due to turbulence, the pilot requested a deviation from air traffic control (ATC) on the south side of a squall line, which ATC provided. Using on-board weather radar, the pilot determined that he needed a greater deviation to the south and made several urgent requests for a clearance to deviate. ATC was not able to approve the deviation requests. ATC instructed the pilot to descend to from FL 240 to FL 200. During the descent, the airplane encountered the first of four 15- to 20-second severe turbulence events, with a 5- to 10-second interval between events. During the events, the pilot made several urgent requests for a deviation, but ATC was not able to approve the requests. As far as the pilot was aware, all the passengers were in their seats with seat restraints on during the turbulent portion of the flight. One of the passengers was an elderly man, and one was his caregiver. The caregiver reported that she had gotten out of her seat to assist the elderly man to adjust his restraints more firmly. During the time she had gotten up to assist, she was thrown about the cabin during the turbulence. The pilot landed the airplane as soon as possible in Madison, Wisconsin, and the caregiver was treated at a local hospital for bone fractures to her right arm.