probator
Webster's Dictionary (GCIDE)
Probator \Pro*ba"tor\, n. [L.]
1.An examiner; an approver. --Maydman. [1913 Webster]
2.(O. Eng. Law) One who, when indicted for crime, confessed it, and accused others, his accomplices, in order to obtain pardon; a state's evidence. [1913 Webster]