The Pennsylvania Superior Court has held that in the absence of an understanding and comprehension of an oath, and the Divine punishment it implies, minor witnesses are incompetent to testify.
Commonwealth v. Rimmel, 221 Pa. Super. 84, 289 A.2d 116 (1972).
Criminal Law - Evidence - Competency of Minor Witness - Obligation of Oath,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol11/iss4/13