They found records for about four thousand lynchings, roughly eight hundred more than in previous counts.
Previous counts have suggested a much lower toll (although earlier work by the same researchers found a high death rate).
There were still many thousands, she said, but they were more sparsely spread than previous counts had recorded in the 1980s.
A fourth charge, that she used fire to commit the three previous counts, would add 10 years to any guilty verdict.
Frank Herhold, of the Marine Industries Association of South Florida, says that nearly 500 such boats are currently being built, up by 70% since the previous count in 1997.
He also credited the increased population figures, in part at least, to the city's "detective work," which provided the census takers with more than 370,000 household addresses added during the past decade or missed in previous counts.
Drawing on small-town newspaper and court archives, along with interviews of local historians and victims' descendants across the South, "Lynching in America" tallied four thousand and seventy-five lynchings, at least eight hundred more than any previous count.
The study argues that the inaccuracy of previous counts means that biologists know less than they think and concludes that grizzly numbers appear to have increased simply because government biologists are working harder to count the bears.
The indictment today, which supersedes the previous counts, did not identify the complainants, but lawyers knowledgeable about the case said the charges referred to the Busa accusations and to those, also previously known, that have been made by Gregory Ford, Anthony Driscoll and a man who, the lawyers said, does not want to be identified.
