Que tal Marcos? No estoy 100 por ciento seguro pero creo que ese termino sería "Legal expert" o "Judicial expert".

Hola Marcos, es una buena pregunta. I believe this is an "EXPERT WITNESS" . These are folks often brought into a courtroom to offer their professional opinion on matters before the court. They typically are not lawyers, but could be experts on Cars (if it were a case regarding a lawsuit against a car manufacturer). The list goes on, and I hope this helps. If you'd like me to write this in Spanish, just let me know.