Defendant first assigns as error the trial court’s summation of the evidence in its jury instructions. We find no error.
The basis of defendant’s argument is that the trial court gave the jury a detailed summary of the State’s evidence, but failed to summarize any evidence favorable to defendant elicited by defendant on cross examination.
The trial court is not required to fully recapitulate all the evidence, but when it does, the trial court must summarize the evidence in the case that is favorable to defendant even though defendant presents no evidence. State v. Sanders, 298 N.C. 512, 259 S.E. 2d 258 (1979), cert. denied, 454 U.S. 973 (1981). G.S. 15A-1232 requires the trial court to summarize the evidence of both parties only to the extent necessary to explain the application of the law to the evidence. State v. Moore, 301 N.C. 262, 271 S.E. 2d 242 (1980). Evidence favorable to defendant elicited on cross examination that tends to exculpate defendant is substantive evidence. State v. Sanders, supra. A trial court cannot adequately explain the application of the law to the evidence in such a case without mentioning the exculpatory evidence elicited by defendant on cross examination. State v. Moore, supra.
Here, defendant presented no evidence at trial and claims that the trial court failed to summarize evidence favorable to defendant elicited from State’s witnesses on cross examination. However, our examination of the record indicates that defendant on cross examination did not elicit substantive evidence tending to exculpate himself. Rather, defendant’s cross examination attempted to impeach the testimony of the State’s witnesses. Testimony which merely tends to impeach or show bias is not substantive in nature and need not be summarized. State v. Abdullah, 309 N.C. 63, 306 S.E. 2d 100 (1983). Here, the evidence defendant claims is favorable to him includes the inability of an expert witness to positively conclude that defendant made the bite marks in question and prior inconsistent statements by other witnesses. This is all testimony which tends to impeach or show bias in the State’s witnesses. It is not substantive in nature and would not exculpate defendant if believed. Accordingly, the trial *441court adequately related the application of the law to the evidence without being required to mention the evidence elicited by defendant on cross examination.
 Defendant next assigns as error the sufficiency of the evidence to support a finding beyond a reasonable doubt that defendant was the perpetrator of the crimes. We find no error.
Defendant argues that the State’s evidence failed to establish the identity of the assailant and that, at best, the State’s evidence raises only a “suspicion or conjecture” that defendant was the assailant. State v. Cutler, 271 N.C. 379, 156 S.E. 2d 155 (1967); State v. White, 293 N.C. 91, 235 S.E. 2d 55 (1977); State v. Bell, 65 N.C. App. 234, 309 S.E. 2d 464 (1983), aff’d, 311 N.C. 299, 316 S.E. 2d 72 (1984). The identity of defendant as the assailant is, of course, a necessary element of each crime charged and must be proven by the State beyond a reasonable doubt. Before submitting the evidence to the jury, the trial court must consider whether there is substantial evidence of each element of the crimes charged. Substantial evidence is such relevant evidence as a reasonable mind might accept as adequate to support a conclusion. State v. Brown, 310 N.C. 563, 313 S.E. 2d 585 (1984); State v. Smith, 300 N.C. 71, 265 S.E. 2d 164 (1980).
Defendant only assigns as error the element of identity of defendant as the victim’s assailant. Based on the record before us, we hold that there was substantial evidence from which the jury could conclude that defendant was, in fact, the assailant.
The evidence presented by the State, although circumstantial, tends to identify defendant as the perpetrator. The victim described the assault and identified her assailant’s race, height and clothing. One State’s witness testified that he saw defendant’s car parked near the victim’s home on the morning of the attack. Another witness testified that he saw defendant standing on the grass near the victim’s front door on the morning in question and that he saw defendant get into his car and drive away. Further evidence showed that the semen left on the rug and a blood sample taken from defendant revealed that both samples were from an individual who was a blood type “O”, type 1 secretor, a blood type found in 28% of the population in North Carolina. In *442addition, the State presented evidence from two forensic odon-tologists. Dr. Webster testified that he was able to identify a total of seventeen points of bite identification, eight of which came from the victim’s shoulder wound. Dr. Souviron testified that he noted ten of the most obvious points of identification. Bite mark identification, approved in other jurisdictions, was first approved in North Carolina in State v. Temple, 302 N.C. 1, 273 S.E. 2d 273 (1981). In that case, Dr. Webster, the same expert who testified here, testified as to eight points of identification between overlays of defendant’s teeth and bite marks on the victim. Here, Dr. Webster identified a total of seventeen common points of identification, eight of which were from one wound. In State v. Green, 305 N.C. 463, 290 S.E. 2d 625 (1982), Dr. Webster again testified as to bite marks, finding fourteen common points of identification between defendant’s teeth and the bite marks on the victim’s arm. Our Supreme Court stated in Green, “we find no reason to suspect that the methodology employed by this expert witness [Dr. Webster] was anything less than scientifically sound and reliable.” Id. at 471, 290 S.E. 2d at 630. We agree. Here, the evidence shows that in addition to a positive comparison of defendant’s teeth with the bite marks by Dr. Webster, there is evidence that the dental casts were identical representations of the teeth of defendant and testimony that the bite marks, represented in photographs of the victim, were “similar and identical” to the dental cast. Based on the record before us, we cannot say that the State’s evidence raised “only a suspicion or conjecture that the accused was the assailant.” State v. Cutler, supra; State v. Bell, supra. Rather, we believe that when taken together and considered in the light most favorable to the State, there is substantial evidence from which the jury could conclude that defendant was the assailant and committed the crimes charged. Accordingly, we find that defendant received a fair trial free of prejudicial error.
Defendant’s assignments of errors numbered 1, 2, 3, 4, 5, 9 and 10 were not brought forward and argued in defendant’s brief and are therefore deemed abandoned. State v. Franks, 300 N.C. 1, 265 S.E. 2d 177 (1980). Rules 28(a), 28(b)(5), Rules of Appellate Procedure.
Judges Whichard and Johnson concur.