Like all witnesses, children must meet three requirements before testifying. First, the child must have certain cognitive and moral capacities; second, the child must have personal knowledge of relevant facts; finally, in most States, the child must take a religious oath or a secular affirmation. Regarding the cognitive and moral elements of testimonial competence, children must have the capacity to observe, sufficient memory, the capacity to communicate, the ability to distinguish the truth from a lie, and an understanding of the obligation to tell the truth in court. To testify as a witness, a person must have personal knowledge of relevant information. In every State, the trial judge is responsible for deciding whether or not children are competent to testify. In contemporary law, States adhere to one of three approaches to children's testimonial competence: presumptive incompetence below a specified age, every person is competent regardless of age, or guaranteed competence in sex offense cases. In rare cases, a child's testimonial competence may be sufficiently in doubt that the judge requires the child to be examined by a mental health professional. 71 footnotes