Idaho Code § 9-201

All persons, without exception, otherwise than is specified in the next two (2) sections, who, having organs of sense, can perceive, and, perceiving, can make known their perceptions to others, may be witnesses. Therefore, neither parties nor other persons who have an interest in the event of an action or proceeding are excluded; nor those who have been convicted of crime; nor persons on account of their opinions on matters of religious belief; although in every case the credibility of the witness may be drawn in question, by the manner in which he testifies, by the character of his testimony, or by evidence affecting his character for truth, honesty or integrity, or his motives, or by contradictory evidence; and the jury are the exclusive judges of his credibility.