232 HARVARD LAW REVIEW. AN UNSETTLED POINT OF EVIDENCE. 1 HOW FAR CAN A WITNESS-TO-VALUE DETAIL OTHERWISE IN- ADMISSIBLE SALES AND APPRAISALS ON WHICH HE FOUNDS HIS OPINION? IN the trial of cases involving the value of real property, wit- nesses who are personally acquainted with the subject, and who are capable of forming an opinion, are allowed to give in evidence their opinion of the property's value ; and are generally allowed to go even farther, and give the grounds for their opinion. It has been customary for counsel to take advantage of this license to introduce as evidence much irrelevant matter in aid of their case, which would be unhesitatingly ruled inadmissible if offered on any other plea. No class of witnesses is more partisan in its testimony than these witnesses-to-value, since in establishing the side of the case they are called on, they also establish the accuracy of their own opinion; and, accordingly, it is usual for such a witness, in response to the request of counsel to " state the grounds on which he bases his opinion," to drag into the case all the sales, appraisals, tax valuations, or other facts, rumors, or fancies, that he believes will be useful to prop up his opinion, or that he has been told will be useful to his side of the case. While the inferior courts have occasionally excluded such de- tails, they have more often admitted them, and have thus allowed the admissibility of this sort of testimony to become more or less firmly established in practice, in total opposition to the common- law theory of evidence, and with the practical result of hopelessly confusing juries, who quite naturally assume that if the evidence is good enough to found the opinion of the witness on, it is good enough to found a verdict on. Some examples that have lately come under my notice in the Superior Court of Massachusetts will serve to illustrate the point. In one case the presiding judge ruled that a witness-to-value, in 1 Since the above article was sent to us for publication, the point under discussion has been settled in Massachusetts in accordance with the view advocated by the article. See Hunt v. Boston, 152 Mass. 168. — Eds.
