the set of trees, the car rotated causing damage on the right side of the car * * * where the damage goes from the front of the automobile to the back of the automobile * * * So based on that, and based on the photographs, my inspection, it is clear to me that the car was impacted by another car, causing it to veer off the road". "It is settled and unquestioned law that opinion evidence must be based on facts in the record or personally known to the witness" ( Cassano v. Hagstrom, 5 N.Y.2d 643, 646). "While it is true that in many cases the cause or effect of a physical injury can be proved in no other way than by the opinions of experts specially qualified by experience and study, it is equally true that such opinions, to be of any value, must be based upon facts in evidence, and either known to the witness or assumed to be true" ( Marx v. Ontario Beach Hotel Amusement Co., 211 N.Y. 33, 39; see, also, Weibert v. Hanan, 202 N.Y. 328, 331; Mohr v. Long Is. Light. Co., 51 A.D.2d 1053; Cross v. Board of Educ., 49 A.D.2d 67, 70). That is not to say that an expert may not offer an opinion unless he has personally viewed the items on which he bases that opinion.

While expert testimony must be based on facts supported by the evidence (Cassano v. Hagstrom, 5 N.Y.2d 643, rearg denied 6 N.Y.2d 882), the facts need only be "fairly inferable" from the evidence (Tarlowe v. Metropolitan Ski Slopes, 28 N.Y.2d 410, 414; Cross v Board of Educ., 49 A.D.2d 67, 70). Such was the case here.

In formulating his opinion that the damage to plaintiff's spinal accessory nerve resulted from causes other than defendant's negligence in performing the surgery, Dr. Cohen relied, to a large extent, upon the erroneous assumptions in the hypothetical questions propounded by defense counsel that examinations by three physicians at Downstate revealed that plaintiff was able to use her trapezius muscle approximately 11 months after the operation. Therefore, the opinion of the only expert witness called by the defense was not properly accepted for consideration by the jury, as it was grounded in speculation rather than an adequate factual basis on the record (see Lipsius v. White, 91 A.D.2d 271, 279, supra; Matter of Aetna Cas. Sur. Co. v. Barile, 86 A.D.2d 362; Cross v. Board of Educ., 49 A.D.2d 67, 70; Filanowicz v. Guarino, 27 A.D.2d 666). Additionally, the Trial Judge erroneously permitted defense counsel to take advantage of his cross-examination of plaintiff's witness, Dr. Antunis, to call the jury's attention to highly prejudicial distortions and misrepresentations of the testimony and medical records of Dr. Phelps (see Zeleznik v. Jewish Chronic Disease Hosp., 47 A.D.2d 199, 207-208; Diaz v. Williams, 22 A.D.2d 873). Defense counsel reinforced the prejudicial impact of those distortions of important evidence presented to the jury when he repeatedly referred to the alleged findings of Dr. Phelps and his colleagues at Downstate throughout his summation (see Diaz v Williams, supra; Fuller v. Hudson Transp. Co., 275 App. Div. 985; Regan v. Frontier Elevator Mill Co., 211 App. Div. 164; cf. Taggart v. Alexander's, Inc., 90 A.D.2d 542).

Thus, we conclude, upon the particular record before us, that the third-party plaintiffs have made a prima facie showing of a defect in the steering mechanism of the Melvey vehicle. While Owens' negligence in apparently driving at an excessive rate of speed obviously contributed to the severity of the injuries and damage, the most reasonable probable cause of the car's swerving off the road was a defect in the steering mechanism, or so the jury could find (cf. Cross v Board of Educ., 49 A.D.2d 67). Hopkins, Acting P.J., Martuscello, Damiani and Titone, JJ., concur.

A plaintiff's expert's opinion is based on facts upon which his opinion is established or "fairly inferable" from the evidence. (Tarlowe v. Metropolitan Ski Slopes, 28 NY2d 410; Cross v. Board of Education, 49 AD2d 67). A plaintiff's expert's determination based on the stained concrete and ceiling ties, as well as the deteriorated basin, is within the expertise of a physical engineer.

Expert testimony must be based on "facts supported by the evidence" or on facts "fairly inferable from the evidence." Cassano v. Hagstrom, 5 NY2d 643, 646 (1959); Gilleo v. Elizabeth A. Horton Mem. Hosp., 196 AD2d 569, 570 (2d Dep't 1993); Cross v. Bd. of Educ., 49 AD2d 67, 70 (2d Dep't 1975); see also Romano v. Stanley, 90 NY2d 444, 451, 661 NYS2d 589, 592 (1997); Amatulli v. Delhi Constr. Corp., 77 NY2d 525, 533 n. 2, 569 NYS2d 337, 341 n. 2 (1991); Hambsch v. New York City Transit Auth., 63 NY2d 723, 725, 480 NYS2d 195, 197 (1984). In the instant matter, plaintiff's experts based their opinions and models on unrealistic assumptions.