In the US the he jury is not tasked with interpreting what the requirements of the law are or tasked with producing/deciding allowed evidence on the case. In these matters the judge will run the court proceedings to produce allowed evidence + arguments and separately instruct the jury on matters of the law pertaining to the case. The role of the jury is just to weigh whether the evidence presented to them seems strong enough to meet the balance of probabilities or be beyond a reasonable doubt (depending on the type of case). I.e. the jury is tasked with answering questions like "based on the evidence presented is it reasonable to doubt the attack was committed by this person" but not tasked with answering/coming up with questions like "what laws would this attack break and how" or "is that question/evidence allowable in the case". Once the jury reaches a verdict it goes back to the judge to decide the sentencing.

Things like https://en.wikipedia.org/wiki/Jury_nullification do exist though, not by procedure but just because the rules can't prevent it, but it's more restricted than many realize and also extremely rare.

It's also true that the Jury isn't flying blind. The judge provides instructions as to how the law applies. It's of note a lot of appeals center around the judges instructions. And fundamental a jury places a hard limit on the states power. Which is to say a judge can and sometimes does limit it even further. Jury can say guilty on charge 4. Judge can say not guilty on charge 4.

Why bring in people with no experience to judge that sort of thing? Whether evidence is convincing is not so easy to decide.

Invent a class of legally informed people who can be paid to think about such things and gather experience in it over time.

Sure, make them separate from the judges so it's not all one guy deciding.

It doesn't necessarily help to be legally informed or not unless you change the role of the jury completely. The law is already set and interpreted by other parties, the only question is about if the jury feels an open ended threshold of doubt has been reached. One could argue to have a class of people that try to rigorously decide what is reasonable doubt based on additions to law that try to quantify doubt but one could just as easily argue finding what society finds to be reasonable doubt is something better answered by normal people instead of a special class and trying to codify what doubt is for every situation in every law unreasonable to do accurately and keep up to date.

I don't think one is inherently right or wrong, it's more a match to ideals. The important thing to note with the current jury system in the US is it's actually preferred they aren't specially informed in law (beyond their given role on the jury) as anything related to legal interpretation is supposed to be done by the rest of the court anyways.

>Invent a class of legally informed people who can be paid to think about such things and gather experience in it over time.

lawyers are legally informed people who are taught how to convince a judge about how the facts explain a certain fact. the judge has to accept the reasoning of one lawyer or the other so the judge needs to be equal to both.