Sec. 49. Opinion of expert witnesses. — 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. (Rule 130, Rules of Court)

When is an expert evidence admissible?

Expert evidence is admissible only when:

1.  The fact to be proved is one requiring expert knowledge
2.  The witness has been qualified as an expert.


What is meant by "qualifying the witness"?

It means proving that the witness presented is an expert and this is done by asking him preliminary questions as to his education, training, experience and the like.


Is the use of opinion of an expert witness mandatory on the part of the courts?

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. (Tabao vs. People, G.R. No. 187246, July 20, 2011)


Are the courts bound by the testimony of the expert witness?

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. (Tabao vs. People)


Cases:

Punzalan vs Comelec
G.R. No. 126669. April 27, 1998

Expert opinions are not ordinarily conclusive in the sense that they must be accepted as true on the subject of their testimony, but are generally regarded as purely ADVISORY; the courts may place whatever weight they choose upon such testimony and may reject it, if they find that it is inconsistent with the facts in the case or otherwise unreasonable.


Tabao vs. People 
G.R. No. 187246, July 20, 2011

The petitioner likewise claims that the CA violated Section 49, Rule 130 of the Revised Rules of Court when it disregarded the testimony of defense witness Police Senior Inspector Danilo Cornelio who testified that the petitioners car could not have bumped the victim because the latters body was not thrown in line with the car, but on its side. The petitioner argues that P/Sr. Insp. Cornelio is highly qualified in the field of traffic accident investigation, and as such, his statements are backed-up by [the] principles of applied physics, engineering, and mathematics.

The petitioners arguments fail to convince us.

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 in accordance 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.

We emphasize that P/Sr. Insp. Cornelio was not an eyewitness to the incident; his testimony was merely based on the Traffic Accident Report prepared by SPO4 Edgar Reyes who himself did not witness the incident. At any rate, nowhere in P/Sr. Insp. Cornelios testimony did he conclusively state that the petitioner could not have been involved in the incident. He did not discount the possibility that the victim could have been thrown on the side. He likewise admitted that the location of an accident victim in relation to the vehicle would also depend on the speed of the vehicle and the point of impact.


US vs Valentin Trono
G.R. No. 1344, January 19, 1904,  3 Phil 213

Facts: Trono et al. were accused of ill treatment of three persons arrested, as a result of which one died. Defense admits the fact of arrest but denies ill treatment. Dr. Icasiano testified to the effect that the deceased had not died due to wounds but by hepatic colic, a disease suffered by the deceased for a long time.

Held: We can not give any credit to the testimony of this physician because the facts which would serve as a foundation to his conclusion are manifestly inexact.

In the first place, in his certificate on folio 18, it is stated that the body of the deceased only showed two small bruises on the superior part of the left iliac region. The witness Esteban Perez testified that the deceased had bruises and swellings on the superior part of the left hand, on the neck, on the ribs, and on the abdomen; Raymunda Perez affirms having seen bruises on the abdomen on both sides, on the left arm, and on the left side of the neck; and Candelaria de los Santos likewise saw them on the upper part of the left hand on the left side of the neck and on the ribs. In the second place, the physician affirms that the deceased devoted himself on the night of the occurrence to his customary libations. Nothing is shown in the case to corroborate this illegal habit, and especially nobody testified to having seen the deceased drunk on the night of the occurrence.

In the third place it is stated in said certificate of the physician that the deceased, after the blows the effects whereof are being inquired into went on foot to the town from a distant barrio, and vice versa. This is manifestly untrue, because the proof in this case shows that from the place where the deceased was ill-treated he was compelled to walk, being supported by a policeman until he reached the town, and in order to take him from the town to his home it was necessary to use a boat.

These last statements are so unjustified that the physician, Icasiano, when testifying, withdrew them during the trial. Why, then, did he set them forth in the certificate which appears on folio 18?

There is nothing in the case to show that the deceased had ever suffered from hypertrophic cirrhosis. The ailment which the deceased had at the time referred to by the physician, Icasiano, was cholera, according to the mother of the deceased, Candelaria de los Santos, who testified, besides, referring to the time to which this case refers, that her son was of a robust constitution and sufferred no ailments whatever.

There are, besides, the following facts to be taken into consideration: After the physician, Icasiano, had examined the deceased, and while the latter was still alive, he told Raymunda Perez that the deceased was suffering from blows with a rifle.

When the death had taken place, the family of the deceased repeatedly requested the physician, Icasiano, to examine the body, which the latter flatly refused to do, and warned them, on the other hand, to bury him quickly, under the pretext that he had died of cholera.

It likewise appears from the testimony of Raymunda Perez that said physician is an intimate friend of the accused, Maximo Angeles.

Expert testimony no doubt constitutes evidence worthy of meriting consideration, although not exclusive, on questions of a professional character. The courts of justice, however, are not bound to submit their findings necessarily to such testimony; they are free to weight them, and they can give or refuse to give them any value as proof, or they can even counterbalance such evidence with the other elements of conviction which may have been adduced during the trial. In the present case there are to be found sufficient data which show in a conclusive manner the seriousness of the wounds inflicted upon the deceased, which from the very first moment prevented him from keeping on his feet, and caused him continuous and sharp pains in the abdomen and retention of the urine — symptoms which constantly showed themselves until death came — which in the absence of satisfactory proof to the contrary may be attributed to these causes, which undoubtedly were sufficient in themselves to bring about the death of the deceased.