Which of these led to the development of democratic principles and was a right of all Roman citizens?

To be tried by a jury

Explanation:

jury trial, or trial by jury, is a lawful proceeding in which a jury makes a decision or findings of fact. It is distinguished from a bench trial in which a judge or panel of judges makes all decisions.

jury is made up of a panel of 12 people who are selected during the empanelment process. In essence a jury comprises of randomly selected members of the public. When all of the evidence has been heard at a trial the jury bears the task of determining whether or not the accused is guilty or not guilty of the charges.

The right to have children of any such marriage become Roman citizens automatically. The right to have the legal rights of the paterfamilias of the family. The right not to pay some taxes, especially local taxes. The right to sue in court and be sued.