How did the 12-0 unanimous decision in Criminal Juries begin?

Question

I don't believe it's spelled out in the Constitution. Do all U.S. states have that standard and why? Why not 11-1 or 10-2? Can individual states legislate a different number other than unanimous?

Answer 1

Various jurisdictions do not require unanimous jury verdicts in criminal matters. For that matter, they do not necessarily require 12 person juries. Some require only 6 or 9.

The institution of trial by jury has its origins in the Magna Carta, which provided that “no free man shall be seized or imprisoned, or stripped of his rights or possessions, or outlawed or exiled, or deprived of his standing in any other way, nor will we proceed with force against him, or send others to do so, except by the lawful judgment of his equals or by the law of the land.”1 Although the Magna Carta did not specify the number of peers necessary to comprise a jury, Sir Edward Coke’s various treatises on the laws of England established that the common practice was to impanel juries of which “the number of noble men that are to be triers are, 12, or more”2 due ostensibly
because “the number of 12 is much respected in holy writ, as 12 apostles, 12 stones, 12 tribes, etc.” Although the number can be traced back to the very
early times of common law, some contemporary courts question the utility of 12 jurors as compared to a smaller jury of eight or six.

For an interesting article on jury size see:

http://www.ncsconline.org/juries/CAJURYREP.pdf

Maybe, size DOES matter!!