The witness, a particeps criminis in respect to the burning, having been examined as a witness on the part of the Commonwealth, and having testified to the guilt of herself and of the defendant, was asked on cross-examination as to a previous confession by her of such guilt, and stated that she had made such confession to an officer, and that she was induced to do so by promises on his part of protection and favor. She also still maintained that her confession, though procured by such promises, was true. The argument, however, would be open to the defendant, that her confession, if so procured, was not true; that she had been induced by the promises to commit herself to a confession which was false; and that, if her confession was false, her present testimony to the guilt of the defendant was also false. The connection between her confession and her present testimony was such, that this argument would be a fair one for the consideration of the jury. Selling a confession would be a legitimate ground for distrusting its truth. She declared virtually that her confession was sold. It thus became material to know if she was in fact induced to make the confession by *404promises. If she was, the weight of her present testimony to the defendant’s guilt was impaired. If she was not, and if her confession was voluntary, her testimony to his guilt was strengthened. The defendant introduced this issue, seeking to obtain the legitimate advantage of the implied impeachment of the witness. It was proper to allow the government to meet the issue, by showing that the confession was voluntary. It is always competent, and often important, to ascertain the motive or bias under which a witness testifies. Everything which goes to affect his credit, as to the particular facts to which he is called to testify, is material and admissible. Commonwealth v. Hunt, 4 Gray, 421. Day v. Stickney, 14 Allen, 255. The testimony of the witness, that her original confession was made under a strong motive or' bias, being material, it was competent for the goverment to contradict it. Pub. Sts. c. 169, § 22.
Exceptions overruled.