One who is legally qualified to be heard to testify in a cause. A person who meets the test of age, mental power, religious belief (under old requirements), and capacity to understand the nature and obligation of an oath.
Credibility is a jury question, whereas competency is a 'threshold question of law to be answered by the judge.' United States v. Martino, 648 F.2d 367, 384 (5th Cir.1981), cert. denied, 456 U.S. 943, 102 S. Ct. 2006, 2007, 72 L. Ed. 2d 465 (1982).