 
In Roman law, the Latin adjective privatus makes a legal distinction between that which is "private" and that which is "publicus", "public" in the sense of pertaining to the Roman people ("populus Romanus").
Used as a substantive, the term "privatus" refers to a citizen who is not a public official or a member of the military. Increasingly throughout the Middle and Late Republic, the "privatus" was nevertheless sometimes granted "imperium" during a crisis; the definition of crisis was elastic, and the amassing of power by unelected individuals (privati) contributed to the breakdown of the checks and balances of the republican system.
Legal terms.
Iudex privatus.
The "iudex privatus" was a sole arbitrator or lay judge who conducted a civil case to which the parties had consented and who usually nominated him. In the event that the parties could not agree on a judge, he was chosen from an official list of potential judges drawn up by the praetor. He was also called a "iudex unus".
References.
 ;templatestyles src="Reflist/styles.css" / ;