Born in North Dakota in 1904, Still was considered one of the most influential of the American post-World War Two abstract expressionist artists, although he was not as well known as others such as Jackson Pollock.
Still died in 1980, and the city of Denver worked for years with his widow, Patricia, to secure the single-artist museum. She died in 2005, and her husband's collection was bequeathed to the city.
Tisch will be formally advised of the charges on Friday, Kimbrough said.
(Editing by Dan Whitcomb and Cynthia Johnston)