Alaska Comm. R. Evid. 603
Rule 601 requires that a witness be capable of understanding the duty to tell the truth. This rule requires the witness to express a willingness to undertake that duty before testifying. The purpose behind requiring an oath or affirmation is to insure that every witness gives accurate and honest testimony.
In earlier times the purpose of the oath, to deter false testimony, became overshadowed by a second use: to exclude qualified witnesses who were not of "proper" religious persuasions and who, therefore, were morally incapable of truthtelling. However,
It came gradually to be perceived that the use of the oath, not to increase testimonial efficiency, but to exclude qualified witnesses, was not only an abuse of its true principle, but also a practical injustice to suitors who needed such testimony. This injustice is clearly enough seen today; but its perception was naturally slow in coming so long as in the community at large the profession of belief in deism or atheism was associated closely with the notion of moral defects.
Wigmore § 1827, at 414.
This rule permits affirmation by a witness as an alternative to swearing an oath. This alternative was provided for in Alaska R. Civ. P. 43(d), superseded by this rule, and has been generally recognized throughout the United States. See Uniform Rule 18 (1953); Kansas Rule 60-418; New Jersey Rule 18; Nebraska Rule 27-603; Maine Rule 603 for similar provisions. By permitting affirmation as well as an oath, many of the difficulties faced by certain religious or other sects should be alleviated. Witnesses should not be barred from testifying because of their religion or the lack of it.
Alaska Comm. R. Evid. 603