[throwawaymaths]

> Juries are generally charged with determining matters of fact

If that is axiomatic, it's not the constitution of the US. I don't know about other jurisdictions, but it's silent on the exact duties of a jury.

[Calavar]

I am not a lawyer, but my understanding is that the idea that juries are for matters of fact comes from English common law. The constitution is a rather barebones framework. There is a lot that it doesn't cover.