We first consider whether the trial judge erred in denying the defendant’s motion to dismiss and his motion to set aside the verdict. “Upon a motion to dismiss, ‘all of the evidence favorable to the State, whether competent or incompetent, must be considered, such evidence must be deemed true and considered in the light most favorable to the State, discrepancies and contradictions therein are disregarded and the State is entitled to every inference of fact which may be reasonably deduced therefrom.’” State v. Jones, 89 N.C. App. 584, 597, 367 S.E.2d 139, 147 (1988) (quoting State v. Witherspoon, 293 N.C. 321, 326, 237 S.E.2d 822, 826 (1977)). The decision to grant or deny a motion to set aside a verdict and for a new trial is within the sound discretion of the trial judge and will be reversed only upon an abuse of discretion. State v. Serzan, 119 N.C. App. 557, 561-62, 459 S.E.2d 297, 301 (1995), cert. denied, 343 N.C. 127, 468 S.E.2d 793 (1996).
A person is guilty of taking indecent liberties with a child under the age of sixteen if he either “willfully takes or attempts to take any immoral, improper, or indecent liberties .. . for the purpose of arousing or gratifying sexual desire,” or “willfully commits or attempts to commit any lewd or lascivious act upon or with the body part or any part or member of the body” of the child. N.C.G.S. § 14-202.1. Taking *689indecent liberties is a specific intent crime. State v. Craven, 312 N.C. 580, 584, 324 S.E.2d 599, 602 (1985). To prove a specific intent crime requires that the State establish that the defendant “acted willfully or with purpose in committing the offense.” State v. Eastman, 113 N.C. App. 347, 353, 438 S.E.2d 460, 463 (1994). The term “willfully” has been defined as an act being done “purposely and designedly in violation of the law.” State v. Whittle, 118 N.C. App. 130, 135, 454 S.E.2d 688, 691 (1995) (quoting State v. Stephenson, 218 N.C. 258, 264, 10 S.E.2d 819, 823 (1940)). However, in indecent liberties cases, a defendant’s purpose in committing the act is “seldom provable by direct evidence and must ordinarily be proven by inference.” State v. Jones, 89 N.C. App. 584, 598, 367 S.E.2d 139, 147 (1988) (quoting State v. Campbell, 51 N.C. App. 418, 421, 276 S.E.2d 726, 729 (1981)).
The State argues that from circumstantial proof that because the defendant committed the touching act against the victim, the jury can infer that the defendant had the requisite intent necessary to commit the crime. In other words, the State argues that from the evidence that defendant touched the victim, a jury could rationally conclude that the defendant woke up, realized the victim was in bed, and formed the intent to touch her “for the purpose of arousing or gratifying [his] sexual desire.” Based on State v. Childress, 321 N.C. 266, 232, 362 S.E.2d 263, 267 (1987), we agree.
The evidence, in the light most favorable to the State, shows that on the night in question, the defendant got into a bed that he and the victim’s mother shared and went to sleep. He was later joined by the victim’s mother who also went to sleep. The victim came to their bed at 12:00 a.m. Defendant touched the victim inside her panties, “rubbed on her,” and put his finger in her vagina. There was no testimony that during the alleged incident, the defendant ever said anything or gave any indication other than the touching that he was awake. Moreover, the victim admitted on cross-examination that she did not know whether the defendant was asleep or awake during the incident. The only testimony regarding the defendant’s intent was Ms. Scher’s testimony that victim told Ms. Scher that, when defendant was confronted by the victim’s mother, he stated that he thought he was touching the mother.
In response to questions at oral argument, the State conceded that the evidence of criminal intent was limited to the evidence that defendant had touched the victim in bed. The State argued vigorously that proof of the improper touching was sufficient to give rise to the inference that defendant was awake and did the touching with the *690intent to gratify his sexual desires. Our Supreme Court has disapproved the notion that in proof of criminal cases, an inference can not be based on an inference. Quoting from Wigmore, Evidence, the Court in Childress noted:
It was once suggested that an inference upon an inference will not be permitted, i.e., that a fact desired to be used circumstantially must itself be established by testimonial evidence, .... There is no such orthodox rule; nor can there be. If there were, hardly a single trial could be adequately prosecuted. (Citation omitted).
There is no logical reason why an inference which naturally arises from a fact proven by circumstantial evidence may not be made. This is the way people often reason in everyday life. In this case the inferences on inferences dealt with proving the facts constituting the elements of the crime. We hold that the jury could properly do this. Insofar as Holland, Byrd, LeDuc and other cases hold that in considering circumstantial evidence an inference may not be made from an inference, they are overruled.
State v. Childress, 321 N.C. 226, 232, 362 S.E.2d 263, 267 (1987) (quoting 1A Wigmore, Evidence § 41 (Tillers rev. 1983)). From the defendant’s touching of the victim and his exculpatory comment to victim’s mother, the State can infer that he was both awake and his purpose was to satisfy his sexual desires. Accordingly, the trial court did not err in denying the defendant’s motion to dismiss.
 We next consider whether the trial court erred in failing to instruct on the mistake of fact defense. Defendant argues that defense counsel requested the mistake of fact instruction be given to the jury and that the trial court’s denial of such an instruction violated the defendant’s right to a fair trial. The defendant in fact asked the judge to instruct the jury that if defendant “didn’t mean to touch the child, he’s not guilty.” In support of this instruction, Ms. Scher testified that the victim stated that when the defendant was confronted by the victim’s mother, defendant stated he thought he was touching the mother. From this request and the evidence at trial, we can infer that the defendant was requesting the mistake of fact instruction. “[A] crime is not committed if the mind of the person doing the act is innocent.” State v. Welch, 232 N.C. 77, 80, 59 S.E.2d 199, 202 (1950). If there is evidence from which an inference can be drawn that the defendant committed the act without the criminal intent necessary, then the law with respect to that intent should be explained and *691applied to the evidence by the court. State v. Walker, 35 N.C. App. 182, 186, 241 S.E.2d 89, 92 (1978).
 Here there was no evidence presented to suggest that the defendant was awake at the time of the alleged incident. In fact, the only evidence we have is that the defendant went to bed and went to sleep before the victim entered his room. Moreover, the only testimony regarding defendant’s intent was victim’s statement to Dottie Scher that when confronted by her mother, defendant stated that he thought he was touching the mother. Because the State presented only circumstantial evidence that defendant was awake and intended to touch the child instead of the mother, the trial court should have instructed the jury as to the mistake of fact defense. Accordingly, the trial court erred in failing to instruct the jury on the mistake of fact defense.
 We next consider whether the trial court committed plain error in failing to instruct the jury on the defense of diminished capacity and unconsciousness. Defendant did not request these instructions but argues that the judge’s failure to instruct constitutes plain error. The defendant said there was evidence that supports the finding that the defendant was asleep and thus these instructions should have been given. Generally, the defendant must object to preserve errors relating to the instructions. However, in exceptional cases, where the claimed instructional error is fundamental, “or where it can be fairly said ‘the instructional mistake had a probable impact on the jury’s finding that the defendant was guilty.’” State v. Odom, 307 N.C. 655, 660, 300 S.E.2d 375, 378 (quoting United States v. McCaskill, 676 F.2d 995, 1002 (4th Cir. 1982), absence of the required instruction, even when there is no objection, will justify reversal under the plain error rule. In order to show the existence of plain error in the trial court’s charge, the defendant must establish that but for the erroneous charge the jury probably would have reached a different verdict. Id. at 661, 300 S.E.2d at 379.
[U]nder the law of this State, unconsciousness, or automatism, is a complete defense to a criminal charge, separate and apart from the defense of insanity; that it is an affirmative defense; and that the burden rests with the defendant to establish this defense, unless it arises out of the State’s own evidence, to the satisfaction of the jury.
State v. Caddell, 287 N.C. 266, 290, 215 S.E.2d 348, 363 (1975). Unconsciousness would be a complete defense because “ ‘[t]he *692absence of consciousness not only precludes the existence of any specific mental state, but also excludes the possibility of a voluntary act without which there can be no criminal liability.’” State v. Jerret, 309 N.C. 239, 264-65, 307 S.E.2d 339, 353 (1983) (quoting State v. Mercer, 275 N.C. 108, 116, 165 S.E.2d 328, 334 (1969)). The earlier cases in which the defendant’s request for an unconsciousness instruction should have been granted have involved defendants who acted as though they were conscious, but for various reasons contend they were in fact unconscious. The test for whether an instruction on diminished capacity is warranted is whether the evidence of defendant’s mental condition is sufficient to cause a reasonable doubt in the mind of a rational trier of fact as to whether the defendant has the ability to form the necessary specific intent. State v. Clark, 324 N.C. 146, 163, 377 S.E.2d 54, 64 (1989).
Here, there is no direct evidence that the defendant was awake at the time of the alleged touching. Even the victim admitted she did not know whether the defendant was asleep or awake. Although our research discloses no case law as to whether being asleep is an appropriate circumstance that requires an unconsciousness or diminished capacity instruction, we conclude that on this record both instructions would be proper. Moreover, had the jury here been instructed that if they found that defendant was unconscious or, more specifically, asleep, they must find defendant not guilty, the outcome of the trial likely would have been different. Accordingly, the trial court erred in failing to instruct the jury on unconsciousness and diminished mental capacity.
 The last issue is whether the trial court erred in admitting the testimony of State’s witness, Dottie Scher. Ms. Scher was called by the prosecution to corroborate the victim’s testimony. “Corroborative testimony is testimony which tends to strengthen, confirm, or make more certain the testimony of another witness.” State v. Rogers, 299 N.C. 597, 601, 264 S.E.2d 89, 92 (1980); see State v. Case, 253 N.C. 130, 116 S.E.2d 429 (1960), cert. denied, 365 U.S. 830, 5 L.Ed.2d 707 (1961). Where testimony which is offered to corroborate the testimony of another witness does so substantially, it is not rendered incompetent by the fact that there is a slight variation. State v. Lester, 294 N.C. 220, 230, 240 S.E.2d 391, 399 (1978). “It is not necessary in every case that evidence tend to prove the precise facts brought out in a witness’s testimony before that evidence may be deemed corroborative of such testimony and properly admissible.” State v. Burns, 307 N.C. 224, 231, 297 S.E.2d 384, 388 (1982).
*693Defendant contends that some of Ms. Scher’s testimony was not corroborative; yet the inconsistencies between the victim’s testimony at trial and the statements made to Ms. Scher were only slight variations. For example, how the victim was lying in bed, when did the incident occur after the victim crawled into bed, and whether the victim switched places with her mother after the incident. These differences fall under the “slight variation” exception to the corroboration rule. The defendant’s main concern, however, is with Ms. Scher’s testimony that the victim told her that the defendant put his finger inside her vagina. The victim’s testimony at trial was that defendant put his hands inside her panties and “rubbed her.” Even though Ms. Scher’s testimony is not specifically what the victim testified to, Ms. Scher’s testimony does strengthen and add credibility to the victim’s testimony. Accordingly, this assignment of error is overruled.
Judges MARTIN, John C., and TIMMONS-GOODSON concur.