We have a system allowing jury nullification. They won't inform you about it officially, but it is both a problem and an essential foundation to the protection a jury provides.
[en.wikipedia.org]

Good question. Prosecutor and defendant (litigants) can each ask a limited number of questions to potential jurors so the litigants can exercise their right to “excuse” a certain individual that they think may be prejudiced to their client. That is voi dire in the jury selection for litigation. Thereafter, the court gives detailed jury instructions setting out each element of the alleged offenses that must be proved by the party bearing the burden of proof and, in a criminal case, that is the prosecution. Does that help?

Same way you trust a judge or magistrate. Individuals may have agendas just as groups do. The possibility of some handpicked strangers having the same agenda is improbable at best.

Which is why I avoid Jury Duty by telling them..."The Lord speaks to me and tells me if the person is guilty or innocent" works every time!!