— The interest of a witness may be proved by his own examination, or by evidence aliunde; but the adoption of either mode of proof, by the party objecting to the competency of the witness, precludes a resort to the other for a like purpose, upon the same ground.
This doctrine, though not clearly settled by the authorities, has been a rule of practice in our own courts; and it is believed to be consistent with a due observance of other settled principles of evidence and practice. A party is not permitted to trifle with the conscience of a witness, when he has other proof that would exclude him, or after having resorted to evidence, to impeach or disqualify him ; nor can he raise collateral issues for that purpose.
The examination of a witness, in respect to his interest, may be either upon the voir dire, or after he has been sworn in chief. But after an unsuccessful attempt to exclude the witness, on this account, his testimony in chief may be stricken out of the case, upon a discovery of his interest. 1 Greenl. Ev. § 423, 424 ; 1 Stark. Ev. 135, 136, and notes.
The instructions to which the exceptions were urged, were correct upon the principles- stated. The witness having been examined upon the voir dire, the subsequent offer to prove his interest, aliunde, was properly rejected.
Exceptions overruled.