Hearsay evidence is inadmissible.

United States v. Barrera-Gonzalez, 950 F.2d 1269, 1273 (10th Cir. 1992) ("We agree with the government's assertion that the terms 'firmly convinced' requires more persuasion than terms such as 'reasonable certainty' or 'abiding conviction as to guilt.' Thus, we hold that the district court's 'reasonable...Courts have occasionally said that proof beyond a reasonable doubt is proof that leaves the trier with a firm and abiding conviction (belief) about the fact in issue.

United States v. Nelson, 419 F.2d 1237, 1240-1241 (9th Cir. 1969) ("Circumstantial evidence in this respect is intrinsically no different from testimonial evidence. Admittedly, circumstantial evidence may in some cases point to a wholly incorrect result. Yet this is equally true of testimonial evidence....Circumstantial evidence is not an inferior grade of evidence: it can be as strong as (or stronger than) any other kind of evidence, including eyewitness evidence, physical evidence, or scientific evidence.

Cf. United States v. Bedonie, 913 F.2d 782, 789-781 (10th Cir. 1990) ("Fed.R.Evid. 601 provides that '[e]very person is competent to be a witness except as otherwise provided.' 'A witness may not testify to a matter unless evidence is introduced sufficient to support a finding that...It is possible that persons may be disqualified from serving as witnesses on grounds not expressly enumerated in codes of evidence or by general common law principles -- on unenumerated grounds such as age, illness, sensory defects, defects in intelligence, lack of understanding, inability to communicate, defects in memory, and inability to be truthful.