logical condition. Mrs. Andrews’ counsel then made a proffer that Dr. Barnes would testify that, in his opinion, Dr. Andrews suffers from deep-seated sexual neuroses, that there are indications of voyeurism and fetishism, that he had a morbid preoccupation with sexual matters involving children, and is not a fit person, morally or psychologically, to have custody of two small boys, and that his opinion is not changed by reason of the fact that there has not been any collection of the material since 1956. The court refused to allow the doctor to give his opinion.
Mrs. Andrews’ counsel also proffered the testimony of Dr. Frank S. Caprio, who was waiting to testify. Dr. Caprio’s qualifications as a psychiatrist were admitted. He is a recognized authority and writer of books on sexual deviations. The proffer was that Dr. Caprio had examined the same material and transcript of Dr. Andrews’ testimony as had Dr. Barnes, that, if asked the same hypothetical question as was put to Dr. Barnes, he would state that he was able to form an opinion as to Dr. Andrews’ present psychological condition, and that, in his opinion, for various reasons which were given, Dr. Andrews is not a psychologically or morally fit person to have custody of the two boys. The proffered testimony was not admitted.
While the admissibility of expert or opinion testimony is largely within the discretion of the trial court, it is subject to review by this Court. Turner v. State Roads Comm’n, 213 Md. 428, 434, 132 A. 2d 455 (1957) and cases therein cited. A qualified medical expert may testify upon hypothetical data alone, without having seen the patient. See State Use of Solomon v. Fishel, 228 Md. 189, *196-97, 179 A. 2d 349 (1962) and Marshall v. Sellers, 188 Md. 508, 517, 53 A. 2d 5 (1957) and authorities therein cited. A medical expert is not barred from expressing an opinion because he is not willing to state it with absolute certainty; it is not certainty but reasonable probability which is the test. Baughman Contracting Co. v. Mellott, 216 Md. 278, 283, 139 A. 2d 852 (1958); Coastal Tank Lines, Inc. v. Canoles,* 207 Md. 37, 45, 113 A. 2d 82 (1955). In a case such as the one before us, psychiatric testimony, if properly presented, could be of material help to the court. The