By her first assignment of error defendant contends the trial court erred in denying her request that her counsel be allowed to ask each prospective juror, rather than the entire panel, the following question: “If the defendant should satisfy you by medical testimony that she was insane at the time of the alleged crime, would you be willing to return a verdict of not guilty even though the evidence would show she did kill her sister?”
We find no merit in this assignment. “. . . [A] motion to examine jurors individually, rather than collectively, is directed to the sound discretion which the trial court possesses for regulating the jury selection process.” State v. Thomas, 294 N.C. 105, 115, 240 S.E. 2d 426 (1978); State v. Young, 287 N.C. 377, 214 S.E. 2d 763 (1975); State v: Jarrette, 284 N.C. 625, 202 S.E. 2d 721 (1974); 8 Strong’s N.C. Index 3d, Jury § 6. We perceive no abuse of discretion in this case.
 By her fourth assignment of error, defendant contends the court erred in not allowing her 14 peremptory jury challenges. This contention has no merit. In State v. Barbour, 295 N.C. 66, 70, *62243 S.E. 2d 380 (1978), this court, speaking through Justice Copeland, said:
“If, ..., it is determined during jury selection in a prosecution for a crime which formerly had been punishable by death that the death penalty may not be imposed upon conviction, the case loses its capital nature, thereby rendering statutes providing for an increased number of peremptory challenges in capital cases inapplicable. United States v. McNally, 485 F. 2d 398 (8th Cir., 1973), cert. denied, 415 U.S. 978, 39 L.Ed. 2d 874, 94 S.Ct. 1566 (1974); Martin v. State, 262 Ind. 232, 314 N.E. 2d 60 (1974), cert. denied, 420 U.S. 911, 42 L.Ed. 2d 841, 95 S.Ct. 833 (1975); State v. Haga, 13 Wash. App. 630, 536 P. 2d 648, cert. denied, 425 U.S. 959, 48 L.Ed. 2d 204, 96 S.Ct. 1740 (1976); People v. Watkins, 17 Ill. App. 3d 574, 308 N.E. 2d 180 (1974). . . .”
See also State v. Clark, 18 N.C. App. 621, 197 S.E. 2d 605 (1973). In this case the district attorney announced at the beginning of the trial that the state would not ask for the death penalty, therefore, this case lost its “capital nature”.
 By her second assignment of error, defendant contends the trial court erred in denying her motion to excuse for cause three prospective jurors who indicated that they would not be willing to return a verdict of not guilty by reason of insanity even though defendant introduced evidence that would satisfy them that she was insane at the time her sister was killed. This assignment has merit.
Defendant properly preserved her exception to the court’s denial of her challenge for cause by (1) exhausting her peremptory challenges and (2) thereafter asserting her right to challenge peremptorily an additional juror. State v. Young, 287 N.C. 377, 214 S.E. 2d 763 (1975); State v. Fox, 277 N.C. 1, 175 S.E. 2d 561 (1970).
Challenges for cause are granted to ensure that defendants are tried by fair, impartial, and unbiased juries. State v. Madden, 292 N.C. 114, 232 S.E. 2d 656 (1977); State v. Williams, 275 N.C. 77, 165 S.E. 2d 481 (1969); State v. Allred, 275 N.C. 554, 169 S.E. 2d 833 (1969). A juror who reveals that he is unable to accept a particular defense or penalty recognized by law is prejudiced to *63such an extent that he can no longer be considered competent. One “who is unwilling to accept as a defense, if proved, that which the law recognizes as such” should be removed from the jury when challenged for cause. 50 C.J.S., Juries § 227, p. 974; see also: 112 A.L.R. 531.
While this court has not previously dealt with the exact factual situation presented by defendant’s second assignment, we have held in analogous situations that jurors who are predisposed with regard to the law or evidence in a case are properly dismissed for cause. In State v. Noell, 284 N.C. 670, 202 S.E. 2d 750 (1974), vacated in part, 428 U.S. 902, 96 S.Ct. 3203, 49 L.Ed. 2d 1205 (1976), three prospective jurors who stated that they could not find defendant guilty even though the state’s evidence should show him guilty beyond a reasonable doubt were held to have been properly excused for cause as they were not impartial and thus could not render a fair verdict. This same principle has been applied in upholding the dismissal for cause of jurors whose conscientious objections to capital punishment precluded them from returning a verdict of guilty in a capital case regardless of the evidence. State v. Squire, 292 N.C. 494, 234 S.E. 2d 563 (1977).
In the case before us those jurors who stated that they could not acquit the defendant even though her insanity was proven to them were committed to disregarding the evidence presented to them as well as the court’s instructions on the law arising from that evidence. The failure of the court to dismiss them for cause, coupled with the subsequent exhaustion of the defendant’s peremptory challenges, forced her to accept a jury which cannot be considered impartial. For this reason she must be granted a new trial.
By various assignments of error defendant raises several issues which evolve from the trial court’s handling of her insanity defense. She first contends that the court erréd in placing the burden of proving insanity on her rather than the state. Secondly, she contends that her motion to dismiss should have been granted because the state failed to offer evidence of her sanity in its casein-chief and failed to rebut the evidence of insanity produced on her behalf. For this same reason, she contends that it was error to instruct the jury on the presumption of sanity.
*64We find no merit in these contentions and hold that the motion to dismiss was properly denied. We also hold that the burden of proving insanity was properly placed on defendant and that the court correctly instructed the jury on the presumption of sanity. 6 Strong’s N.C. Index 3d, Homicide § 7.
Defendant’s motion for dismissal challenges the sufficiency of the evidence to go to the jury. State v. Britt, 285 N.C. 256, 204 S.E. 2d 817 (1974). She acknowledges that a criminal defendant in North Carolina is presumed sane until the contrary is made to appear by evidence produced at the trial. State v. Hammonds, 290 N.C. 1, 224 S.E. 2d 595 (1976). She contends, however, that this rebuttable presumption is dissipated by the instroduction of evidence of insanity and that a motion to dismiss must be granted if the state thereafter fails to produce evidence of the sanity of the defendant.
 We have repeatedly held, and we again reiterate the rule, that the burden of proving insanity is properly placed on the defendant in a criminal trial. Furthermore, a defendant must establish his insanity to the satisfaction of the jury if it is to provide a defense to a criminal charge. State v. Pagano, 294 N.C. 729, 242 S.E. 2d 825 (1978); State v. Caldwell, 293 N.C 336, 237 S.E. 2d 742 (1977); State v. Harris, 290 N.C. 718, 228 S.E. 2d 424 (1976); State v. Hammonds, supra; State v. Caddell, 287 N.C. 266, 215 S.E. 2d 348 (1975); State v. Cooper, 286 N.C. 549, 213 S.E. 2d 305 (1975); State v. Atkinson, 275 N.C. 288, 167 S.E. 2d 241 (1969), rev’d as to death penalty, 403 U.S. 948, 29 L.Ed. 2d 859, 91 S.Ct. 2283 (1971); State v. Swink, 229 N.C. 123, 47 S.E. 2d 852 (1948). The correctness of this rule is reinforced by the holding of the Supreme Court of the United States in Patterson v. New York, 432 U.S. 197, 97 S.Ct. 2319, 53 L.Ed. 2d 281 (1977). There the court held that placing the burden on the defendant of proving the defense of extreme emotional disturbance as defined by New York law did not violate the Due Process Clause of the Fourteenth Amendment to the United States’ Constitution. We likewise find that no unconstitutional burden is imposed upon defendants by the requirement of North Carolina law which compels them to prove the defense of insanity.
Defendant’s argument fails to take into account the effect which placing the burden of proving insanity upon the defendant *65has on the presumption of sanity. . . [T]he prosecution may assume, as the law does, that the defendant is sane. The assumption persists until challenged and the contrary is made to appear from circumstances of alleviation, excuse, or justification; and it is incumbent on the defendant to show such circumstances to the satisfaction of the jury, unless they arise out of the evidence against him. S. v. Grainger, 223 N.C. 716, 28 S.E. 2d 228 (1943). If no evidence of insanity be offered, the presumption of sanity prevails. And where the defendant offers evidence of his insanity, the state may seek to rebut it or to establish the defendant’s sanity by the presumption of law, or by the testimony of witnesses, or by both (emphasis added).” State v. Harris, 223 N.C. 697, 703, 28 S.E. 2d 232, 237 (1943). Even if the evidence of insanity presented by the defendant is uncontradicted by the state, it is the defendant’s burden to satisfy the jury of the existence of the defense. The credibility of the defense witnesses in this case was a proper matter for the jury. A diagnosis of mental illness by an expert is not in and of itself conclusive on the issue of insanity. State v. Taylor, 290 N.C. 220, 226 S.E. 2d 23 (1976); State v. Potter, 285 N.C. 238, 204 S.E. 2d 649 (1974).
Furthermore, the state did not, as defendant suggests, rely solely on the presumption of sanity. Testimony of witnesses who observed the defendant’s actions at the time of the incident was offered. Those witnesses observed that defendant had sufficient presence of mind to flee after the shooting. This fact has been held to raise an inference of sanity. State v. Journegan, 185 N.C. 700, 117 S.E. 27 (1923). In addition, the diagnosis and opinion of each of defendant’s expert witnesses was challenged by cross-examination. This cross-examination focused on the length of time each expert spent in interviewing defendant as well as on the factors which were observed in defendant’s behavior and ultimately formed the basis for the experts’ opinions. This evidence and cross-examination, coupled with the presumption of sanity and the defendant’s burden of proof, make the issue of insanity one which the court was clearly justified in submitting to the jury.
 In charging the jury the trial judge informed them that defendant relied on the defense of insanity, which would be a complete defense to the crime of murder if proven to their satisfaction. He then made the following statement to which the defendant took exception: “I instruct you that sanity or soundness *66of mind is a normal condition of men and women; therefore, everyone is presumed sane until the contrary is made to appear.” The trial judge then stated the test for insanity and again reminded the jury that defendant had the burden of proving the existence of the defense to their satisfaction.
We find no error in this aspect of the charge. The instruction which was given constitutes an accurate and clear statement of the law on an issue raised by the defendant’s plea and the evidence in the case. State v. Watson, 294 N.C. 159, 240 S.E. 2d 440 (1978); G.S. 1-180; 4 Strong’s N.C. Index 3d, Criminal Law § 111-
We deem it unnecessary to discuss defendant’s other assignments of error as they are not likely to recur upon the retrial of the case.
For the reasons stated, defendant is granted a