At The Weekly Standard, David M. Wagner writes:
[Eighty-one] years before the right to vote made its first appearance in the Constitution, the jury right in criminal cases was already included in the unamended Constitution (Article III, Section 2, paragraph 3), as it came from the Philadelphia Convention. But the convention declined to extend this right to civilcases. This alone lost the Constitution the votes of George Mason and Elbridge Gerry, and got the ball rolling on the movement for a Bill of Rights, either as a condition of ratification (constitutional opponents lost on that), or as a top item of business when the new government convened (they won on that; politicians kept promises in those days). And so a guarantee of jury trial in civil cases became the 7th Amendment.
In fact, 3 of the first 10 amendments mention juries: We have grand juries in the 5th, criminal petit juries in the 6th, and civil juries in the 7th. For comparison, the right to vote is nowhere mentioned in the Bill of Rights. A latecomer, as I said.
Perhaps, though, we shouldn’t drive too thick a wedge between jury service and voting. A jury votes, after all. Yale’s Akhil Amar, a major advocate of juries, even suggests that the Framers likened juries to a Parliament in miniature, with the jury analogized to the House of Commons, making the most important decisions, and the judge to the House of Lords, exercising a moderating but rarely reversing power.
To whom did this “jury right” belong? The criminal suspect? The civil plaintiff and defendant? All of these—but also to the citizen who would take a turn as a juror. This was an important element of self-government. Citizens were to have a role not only in making laws (by voting for their representatives), but in enforcing and interpreting them too.