The fact that a witness is not of sound mind does not in itself constitute ground for his exclusion. His testimony can properly be excluded only when his affliction is such that he is unable to retain in his mind a recollection of that which he has seen or heard, and about which he is called to testify, or that he is unable to distinguish between right and wrong. He must, of course, have sufficient mental capacity and understanding to comprehend and appreciate the obligation of an oath, and to give a reasonably accurate statement of what he has seen or heard, bearing on matters at issue in the proceeding on trial.7 The weight to be accorded the testimony of such witness is a question exclusively for the jury.

6 Featherstone vs. People, 194 I11., 325. 7 Cannady vs. Lynch, 27 Minn., 435; Walker va. State, 97 Ala., 85.