Glenn Reynolds taking up the subject of jury nullification cites his paper which includes the origin of the jury. Our law, as tradition has it, is of Roman origin. This is evidenced in the early history of the jury, from the book This Was Cicero by H.J. Haskell 1942 Fawcett/Alfred A Knopf, p. 64
... As litigation increased, it was necessary to create additional courts. By the time Cicero was practicing, there were 2 civil and 6 criminal courts in Rome with elective judges...
The jury wheel was prepared by the presiding judge. The names of the prospective jurors we inscribed in an Album, or White Book... In Roman procedure, all the Senators on duty in Rome were regarded as law lords and their names were inscribed in the Album. Early in Cicero's career the 400 hundred senatorial jurors were supplemented by an equal number drawn from two other divisions of the upper classes: the wealthier business men and perhaps business men of lesser means. The wheel usually included over a thousand names.
Jurors for any particular case were selected form the Album by lot. Challenges were allowed to both sides and the ordinary jury in a criminal case included from 50 to 75 men. It is evident that the large Roman jury more nearly approached a public meeting than the modern jury of 12 men, so that oratorical training was emphasized in the education of an aspirant to the Roman bar.