English to Spanish Law/Patents Law: Patents, Trademarks, Copyright productos farmacéuticos

No pude encontrar, hasta ahora, un solo término o expresión que englobe el significado de fact-finder.
La definición del término sería:
"n. The judge or jury during a trial of a lawsuit or criminal prosecution that decides if the facts presented have been proven. In rare instances, the judge will appoint a special master to investigate certain fact's existence"
Y mi contexto (apelación a un fallo de no obviedad de una reivindicación de una patente):.
"Although an exact definition is elusive, “clear and convincing evidence” has been described as evidence that “place[s] in the ultimate factfinder an abiding conviction that the truth of its factual contentions are highly probable."
"However, the district court’s omission in this case is harmless error because evidence of record easily satisfies us that a reasonable fact-finder could only conclude that XXXXXX has shown by clear and convincing evidence that..."
Mil gracias!