
305 S.E.2d 535 (1983)
STATE of North Carolina
v.
Joseph Daniel KEEN, Jr.
No. 59A83.
Supreme Court of North Carolina.
August 9, 1983.
*537 Rufus L. Edmisten, Atty. Gen. by Daniel F. McLawhorn, Asst. Atty. Gen., Raleigh, for the State.
Tharrington, Smith & Hargrove by Roger W. Smith and Mark J. Prak, Raleigh, for defendant-appellant.
BRANCH, Chief Justice.
By his sole assignment of error defendant contends the trial court committed prejudicial error in failing to strike certain testimony of Dr. J.D. Danoff. We find merit in this assignment and hold that defendant is entitled to a new trial.
Dr. Danoff, a professor in the Department of Psychiatry at East Carolina University School of Medicine, who observed and treated Langley in the Pitt Memorial Hospital for approximately eight days, testified as a witness for the State. It was stipulated that Dr. Danoff was an expert "in the general field of psychiatry with a specialty in the area of adolescent psychiatry." Among other things, Danoff testified that while Langley was in the hospital, he was in an acute anxiety state, was suicidal, angry and hostile. Danoff further testified that emotions commonly associated with the type of incident described by Langley included anxiety, anger, shame, guilt and feelings of worthlessness.
Defendant's assignment of error relates to the following questions, answers and rulings of the trial court:
Q. Doctor Danoff, do you have an opinion based upon your medical training and experience as to whether or not James was fantasizing in any manner in his account of this situation?
Objection.
Court: Overruled; you may answer.
A. Yes, I do.
Court: The answer to that question is yes or no; do you have an opinion?
A. Yes, I do.
Q. What is that opinion?
A. That an attack occurred on him; that this was reality.
Motion to strike.
Court: Motion denied.
Dr. Danoff's answer was not responsive to the question asked by the prosecutor. If an unresponsive answer produces irrelevant or incompetent evidence, the evidence should be stricken and withdrawn from the jury. See State v. Ferguson, 280 N.C. 95, 185 S.E.2d 119 (1971). Dr. Danoff was asked for his opinion whether Langley "was fantasizing in any manner in his account of this situation." Instead of answering the question, the witness stated his opinion "that an attack occurred on [Langley]; that this was a reality."
The evidence provided in the answer was incompetent. G.S. 8-58.13 provides:
If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to *538 determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion.
We think the most reasonable interpretation of the answer given by Dr. Danoff is that, in his opinion, Langley had been "attacked" and that this was a "reality". In so answering, the witness went beyond the point of assisting the jury in determining a fact in issue. He, in effect, expressed an opinion as to the guilt of defendant.
In State v. Brown, 300 N.C. 731, 733, 268 S.E.2d 201, 203 (1980), Justice Carlton, speaking for this Court and relying on State v. Wilkerson, 295 N.C. 559, 247 S.E.2d 905 (1978), an opinion by Justice Exum, said:
[Expert] testimony is properly admitted if
(1) the witness because of his expertise is in a better position to have an opinion on the subject than the trier of fact.
(2) the witness testifies only that an event could or might have caused an injury but does not testify to the conclusion that the event did in fact cause the injury, unless his expertise leads him to an unmistakable conclusion and
(3) the witness does not express an opinion as to the defendant's guilt or innocence. [Footnote omitted.]
In applying the criteria set forth in Brown and quoted above, criteria (1) was unquestionably met since the parties stipulated as to Dr. Danoff's expertise.
It is clear that the witness exceeded criteria (2). He did not testify that Langley's mental state was consistent with that of one who had been sexually attacked, or that an attack as described by Langley could or might have caused his mental state. On the contrary, the witness stated that in his opinion such an attack had been committed on Langley and that "this was reality."
Our conclusion that the witness exceeded criteria (2) in instant case is further supported by Patrick v. Treadwell, 222 N.C. 1, 21 S.E.2d 818 (1942). While Patrick was a civil case involving a physical injury, we think the situation there presented is analogous to the case at bar. In Patrick, the plaintiff, a child, sought to recover damages for alleged injuries resulting from a collision of two automobiles. A short time prior to the collision the child's arm had been broken and set in a cast. It was alleged that in the collision the child was thrown from the seat, her cast was broken, and that fragments of bone were knocked out of place, resulting in permanent injury. This Court held that it was error to permit a doctor to state his opinion that the collision in question caused the fragment of bone to be knocked out of place, or to testify, "I know the accident did it."
We also think that under the evidence in this case, criteria (3) was violated. To find defendant guilty, it was incumbent on the State to prove, and the jury to find, that a sexual offense was committed on Langley and that defendant committed the offense. See State v. Bass, 253 N.C. 318, 116 S.E.2d 772 (1960). Since defendant admitted that he was with Langley at the time in question, and that no one else was present, the only real question for the jury was whether the sexual offense was committed on Langley. Therefore, when Dr. Danoff testified that in his opinion "an attack occurred on him" and "that this was reality", he clearly expressed an opinion as to defendant's guilt.
The remaining question for our consideration is whether the trial court's error in not striking the testimony complained of was prejudicial to defendant. We hold that it was prejudicial.
The test of harmless error "is whether there is a reasonable possibility that the evidence complained of might have contributed to the conviction." Fahy v. Connecticut, 375 U.S. 85, 86-87, 84 S.Ct. 229, 230, 11 L.Ed.2d 171, 173 (1963). Accord, State v. Thacker, 281 N.C. 447, 455, 189 S.E.2d 145, 150 (1972).
In the case at hand, a decision depended primarily on whether the jury believed Langley or defendant. Both proved good reputations and both introduced evidence as to statements they made following the evening *539 in question. That being true, the testimony of Dr. Danoff was crucial and it is probable that the jury gave considerable weight to every part of his testimony. Consequently, we must conclude that there is a reasonable possibility that the challenged testimony might have contributed to defendant's conviction.
NEW TRIAL.
