trier

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One that tries, as in making an effort or in testing something.
• noun Law A judge or jury, as authorized to determine the facts of a legal case based on the evidence submitted by the parties.

from The Century Dictionary.

• noun A tool used in trying, testing, or sampling.
• noun One who tries; one who examines, investigates, tests, or attempts; one who experiments.
• noun Specifically— In English history, a member of a committee appointed by the king, and charged with examining petitions, referring them to the courts, and reporting them to Parliament, if so required.
• noun Under the Commonwealth, an ecclesiastical commissioner appointed by the Parliament to examine the character and qualifications of ministers for institution and induction.
• noun One who tries judicially; a judge.
• noun In law, one appointed to decide whether a challenge to a juror is just. See trior.
• noun That which tries; a test.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who tries; one who makes experiments; one who examines anything by a test or standard.
• noun One who tries judicially.
• noun (Law) A person appointed according to law to try challenges of jurors; a trior.
• noun That which tries or approves; a test.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One who tries; one who makes experiments or examines anything by a test or standard.
• noun One who tries judicially.
• noun law A person appointed by law to try challenges of jurors; a trior.
• noun obsolete That which tries or approves; a test.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun one (as a judge) who examines and settles a case
• noun one who tries