Field, J.
Whether a person, who is offered as a witness, is shown to be qualified to give an opinion upon the value of land, must be left largely to the discretion of the presiding judge. We cannot say, upon the evidence recited in the exceptions, that Mason was not rightly excluded as a witness to value. The case shows that there was no difficulty in obtaining witnesses whose qualifications were unquestioned, and this fact was properly considered by the presiding judge in deciding to exclude him. Tucker v. Massachusetts Central Railroad, 118 Mass. 546, 548.
It was ''also, we think, within the discretion of the presiding judge to admit the question which was put to Wyman by the respondent on cross-examination, to which the petitioners objected. As Wyman’s land was adjoining to and of the same general character as that of the petitioners, sales of it would be competent to prove the value of the petitioners’ land; but the *329opinion of witnesses upon the value of Wyman’s land would nob he competent to prove the value of the petitioners’ land. Wyman v. Lexington & West Cambridge Railroad, 13 Met. 316, 327. Shattuck v. Stoneham Branch Railroad, 6 Allen, 115. When, therefore, the respondent asked the witness Wyman his opinion of the value of his own land, the question should have been excluded, if objection had been made. The question, however, having been answered, without objection, the respondent could not have been permitted to contradict the answer by the testimony of other witnesses, or by other evidence than the testimony of the witness himself. Immaterial or irrelevant issues cannot be raised and tried in this manner. Fletcher v. Boston Maine Railroad, 1 Allen, 9. Shurtleff v. Parker, 130 Mass. 293. But the testimony admitted was relevant to the testimony of the same witness already in evidence without objection, and it was admitted solely on the question of the bias or fairness of the witness. The extent to which the cross-examination of a witness as to credit may be carried must be left largely to the judge presiding at the trial, and if matters which are merely immaterial, or which tend to show the reasons of the witness for his opinions or his fairness' of mind, are admitted in cross-examinatian, there is, as a general rule, no exception. Considerable latitude should be allowed in cross-examining witnesses to value, in order that the grounds of their opinion may appear. Prescott v. Ward, 10 Allen, 203. Smith v. Castles, 1 Gray, 108.
The record of the board of selectmen, of whom Martin was one, was offered for the purpose of contradicting the testimony of Martin. The fact that the record, or certificate, was signed by Martin, as well as by the other selectmen, did not show that the amount of the damages awarded was the sum which Martin, acting on his own judgment, thought ought to have been awarded. Selectmen have no clerk, and their doings can only be certified by their own signatures, and the certificate purported to give, not the opinion of the selectmen individually, but the judgment of the board, which might be the judgment of a majority only of a quorum of the board. Besides, in every judicial or quasi judicial determination of damages by a board composed of more than one person, there must be compromises of individual opinion in order that any result may be reached, and a judicial body *330must give some weight to evidence, and cannot act solely upon the personal knowledge of its members, when evidence is produced before them. Either, then, the record should have been excluded, or, if admitted, Martin and the other selectmen should have been permitted to testify to the part taken, and to the opinions expressed by Martin in the deliberations of the selectmen which resulted in the award. While the deliberations of legislative bodies are usually public, the deliberations of judicial or quasi judicial bodies are private, and there are reasons of public policy why they should not be made public, particularly when the purpose to be served is comparatively unimportant. Grand and petit jurors are not permitted to testify to opinions concerning the case expressed in their consultations with one another, and arbitrators are not permitted to testify to the grounds on which they reached the conclusions declared in the award. Bigelow v. Maynard, 4 Cush. 317. Woodward v. Leavitt, 107 Mass. 453. Commonwealth v. White, 147 Mass. 76. For the purpose of contradicting a witness, we think that evidence ought not to be received of the deliberations of selectmen acting in a quasi judicial capacity, and that the certificate of the doings of the board of selectmen was rightly excluded.
Exceptions overruled.