The witness Mary Jane Perry being only twelve years of age, it was a proper case for the court to inquire as to her competency in reference to her understanding of the nature of an oath, and her responsibility to the Supreme Being, for not testifying to the truth. So far as regards the latter, the answer of the witness was certainly full and satisfactory. It is the nature of the oath as a religious obligation and solemn appeal to God, that is the principal subject of inquiry when an examination of this character is made. To answer this inquiry properly will of course require that the witness have a sufficient degree of intelligence and understanding to be admitted to testify in the matter before the court.
We think the examination of an infant as to his competency to testify, and the determination of the question whether he is competent, are very much under the discretion of the court before whom the case is heard, and not in general a subject of exceptions removing that question to a higher court. If an erroneous view of any legal principle was taken upon such hearing, that might properly be brought before us for revision, but not the judgment of the court as to the sufficiency of the proof to satisfy the court of the ability of the witness to understand the nature of an oath, and of the possession of sufficient intelligence to testify in the case. Commonwealth v. Hills, 10 Cush. 530.
As to the other point raised, it is difficult to perceive any ground for the objection urged to the interrogatory propounded to Dr. Deane by the district attorney on the cross-examination. The question put to the witness presented a hypothetical case, and was answered as such. It did not make the witness a judge of the facts in proof before the jury. It properly left that to be decided by the jury, and the court in their instructions *297guarded the jury on that point, by stating that if the supposed case, upon which an opinion had been given by the witness, included any circumstance not proved, the answer of the witness was to be excluded from their consideration. The case of Woodbury v. Obear, 7 Gray, 467, is directly in point as an authority for this form of putting the question to an expert. In that case, under its peculiar circumstances as to the state of the evidence, a hypothetical case was held to be the only proper form of putting the question to a witness called as an expert.
In no aspect of the present case can these objections prevail.
Exceptions overruled.