OPINION OF AN EXPERT WITNESS:

     Section 49, Rule 130 of the Revised Rules of Court states that the opinion of a witness on a matter requiring special knowledge, skill, experience or training, which he is shown to possess, may be received in evidence. The use of the word “may” signifies that the use of opinion of an expert witness is permissive and not mandatory on the part of the courts.  Allowing the testimony does not mean, too, that courts are bound by the testimony of the expert witness.  The testimony of an expert witness must be construed to have been presented not to sway the court in favor of any of the parties, but to assist the court in the determination of the issue before it, and is for the court to adopt or not to adopt depending on its appreciation of the attendant facts and the applicable law.  It has been held of expert testimonies: Although courts are not ordinarily bound by expert testimonies, they may place whatever weight they may choose upon such testimonies inaccordance with the facts of the case. The relative weight and sufficiency of expert testimony is peculiarly within the province of the trial court to decide, considering the ability and character of the witness, his actions upon the witness stand, the weight and process of the reasoning by which he has supported his opinion, his possible bias in favor of the side for whom he testifies, the fact that he is a paid witness, the relative opportunities for study and observation of the matters about which he testifies, and any other matters which deserve to illuminate his statements.  The opinion of the expert may not be arbitrarily rejected; it is to be considered by the court in view of all the facts and circumstances in the case and when common knowledge utterly fails, the expert opinion may be given controlling effect.  The problem of the credibility of the expert witness and the evaluation of his testimony is left to the discretion of the trial court whose ruling thereupon is not reviewable in the absence of abuse of discretion. (Tabao vs. People, G.R. No. 187246, July 20, 2011, Brion, J.).