D, his female cousin MM, and her younger brother were playing outside their grandfather's trailer on an Indian reservation in Arizona. IMM was twelve years old, MM was six years old, and her brother was five years old. The grandfather went to check on them and found MM standing in front of the boys with her pants down. He yelled at her and asked 'what the hell they were doing,' to which she replied, 'They told me to take my clothes off.' The boys were sitting next to each other on a propane tank and both of them had their clothes on. MM started crying after the grandfather began yelling at her. MM's mother did not check MM for any physical signs of sexual assault, or ever take her to the hospital or the police station for a physical examination. MM did not ever complain of any pain; nor did her mother ever ask her any questions about what P did to her. Instead, MM's mother testified that she called the police. At trial, the mother testified that MM had also said that 'P made her do it.' MM's younger brother also testified at the trial. D requested that a hearing be held to evaluate whether he was competent to testify. He was five years old when he witnessed the incident and was seven years old at the time of the trial. The district judge asked him several questions about 'the difference between . . . telling the truth, and telling a lie.' He correctly answered a series of questions about whether it would have been the truth or a lie for him to make certain statements. Although he was not sure what would happen if he told a lie, he answered 'Yes' when asked, 'Do you understand how important it is for you to tell the truth today?' He also answered 'Yes' when asked, 'And do you know that you could get in trouble if you didn't tell the truth?' Later in the hearing, in response to questions from defense counsel, he confused a 'promise' with a 'secret.' After the district judge questioned him further, he demonstrated that he understood the concept of a promise. The court made a preliminary determination that he was competent to testify and later made that determination final. The younger brother testified that he had seen MM and D 'having sex.' He admitted that he did not know what 'having sex' meant or where he had heard these words before. The boy was confused about a number of issues. But when defense counsel asked if someone had talked to him about the incident and told him what to say, he said yes and stated that his mother had told him what to say. When she testified, his mother stated that she had never spoken with him about what he saw or what had happened that day and that she had never told him what to say in D's case. She then asserted that his statement to the contrary was a lie. P was convicted and appealed in part that the younger brother’s testimony should have been excluded on the grounds that the child could not understand an oath.