Walter Ehrlich, "Scott, Dred," American National Biography Online, February 2000, http://www.anb.org/articles/11/11-00984.html.
Unanticipated developments converted an open-and-shut freedom suit into a cause célèbre. In the trial on 30 June 1847, the court rejected one piece of vital evidence on a legal technicality--that it was hearsay evidence and therefore not admissible--and the slave's freedom had to await a second trial when that evidence could be properly introduced. It took almost three years, until 12 January 1850, before that trial took place, a delay caused by events over which none of the litigants had any control. With the earlier legal technicality corrected, the court unhesitatingly declared Dred Scott to be free.