624.1Bite Mark Analysis
- Bite mark analysis is conducted by comparing a sample (such as a bite mark left on the victim’s skin) to a sample taken from the defendant (through impressions or photographs), and comparing the unique features of both in order to determine whether the defendant left the original mark.
- Bite mark analysis has been allowed into evidence in North Carolina and most other courts for many years; however, recent scientific studies of this field have raised serious concerns about its reliability.
- A sample can be obtained from the defendant for comparison through a search warrant or nontestimonial order.
The theory behind bite mark analysis is that the dental characteristics of size, shape, and arch form mean that each person has a unique and distinctive set of teeth, which leave a correspondingly unique pattern or impression after a bite. By comparing a bite mark that is being investigated (e.g., on the victim’s skin) to the teeth of the person suspected of having committed the crime, a bite mark analyst (“forensic odontologist”) may be able to provide evidence linking the suspect to the crime. To analyze such evidence, a dental expert will usually take photographs (or make an impression) of the defendant’s teeth. The expert should be able to rule out any injuries or wounds caused by objects other than teeth, and differentiate between animal and human bites. In some cases, forensic odontologists have even testified as to a person’s likely age and race based on an examination of his teeth.
To make a good comparison, a balanced, color, scale photograph should be made of the defendant’s teeth (which may be used by the expert to illustrate his or her testimony in court) and of the victim’s bite. See State v. Green, 305 N.C. 463 (1982). Because the dental expert will need to know the scale shown in the picture, it is essential to have some method of measurement (such as a ruler or tape measure) photographed alongside the bite mark and the defendant’s teeth. A plaster cast of the defendant’s dental impressions can also be used to prepare a plastic overlay. The plastic overlay is used to mark the points of contact, and forms a representation of defendant’s bite marks or a pattern of the cutting edges of defendant’s teeth. This representation can then be compared with a scaled photograph of the bite mark on the victim as a means of determining common points of identification.
Any bite marks should also be examined for saliva (by wiping a sterile cotton swab across the bite mark), since it may be possible to determine the DNA and secretor status of the person who made the bite as an alternative method of identification. For more information, see the related expert witness entry on DNA Evidence.
Admissibility and Reliability
Bite mark analysis has historically been recognized as a reliable scientific method of identification in North Carolina courts, and testimony about the analysis has consistently been admitted upon proper authentication and foundation. See State v. Trogden, 216 N.C. App. 15 (2011) (forensic odontologist examined plaster casts of the teeth of the mother, father, two sisters, and the defendant, then compared overlays created by scanning the casts with to-scale photographs of the bite marks on the victim’s arm, and testified without objection that the defendant’s bite, among the five people for whom plaster casts had been made, was the only one that could have made the bite marks); State v. Johnson, 317 N.C. 343 (1986) (allowing witness to use plaster casts of defendant’s teeth and indentations on the deceased’s breast to demonstrate how defendant’s teeth matched the bite marks - evidence was relevant to show that the deceased was the victim of a violent sexual attack, and tending to prove whether it was defendant who inflicted the injury); State v. Carter, 74 N.C. App. 437 (1985) (expert testified that bite marks were “identical to dental casts of defendant’s teeth” based on 17 points of identification, eight of which were from one wound); State v. Green, 305 N.C. 463 (1982) (expert in forensic odontology and bite mark identification was properly permitted to state his opinion that a bite mark on a rape victim’s arm was made by defendant, based on the expert’s comparison of a photograph of the bite mark and impressions made by defendant’s teeth); State v. Temple, 302 N.C. 1 (1981) (allowing an expert witness to testify that the bite marks on the murder victim’s body were made by defendant, when the expert applied scientifically-established techniques of dentistry and photography to determine whether the bite marks were caused by the defendant’s teeth).
Proceed with caution…
Despite the long history of admissibility of bite mark testimony in North Carolina courts (and virtually all other courts), several recent studies have been extremely critical of the technique, and have expressed serious doubts about its reliability. For example, the President’s Council of Advisors on Science and Technology (“PCAST”) 2016 report, Section 5.1, pages 83-87, found that the field “does not meet the scientific standards for foundational validity, and is far from meeting such standards. To the contrary, available scientific evidence strongly suggests that examiners cannot consistently agree on whether an injury is a human bitemark and cannot identify the source of bitemark with reasonable accuracy.” For more information about these reliability concerns, see here and here.
If a prosecutor plans to use bite mark evidence at trial, he or she should expect the defense to request a Daubert hearing and contest the admissibility of the evidence. Even if the court allows the testimony, the prosecutor should expect the witness to be vigorously cross-examined about the validity of the field and its methods. Therefore, before offering such evidence, the prosecutor should carefully weigh the risks and benefits, and consider what effect it may have on the jurors if they conclude that part of the state’s case relies on questionable scientific methods.
There are not yet any post-2011 North Carolina cases examining the reliability or admissibility of bite mark testimony under the revised Rule 702 incorporating the Daubert factors, but trial courts in other jurisdictions have continued to allow bite mark testimony into evidence. See, e.g., Chanthakoummane v. Stephens, 816 F.3d 62 (5th Cir. 2016) (noting in dicta summarizing the evidence in the case that “[a]t trial, the jury heard the testimony of Dr. Brent Hutson, a forensic dentist who examined Petitioner and concluded that ‘within reasonable dental certainty beyond a doubt’ that Petitioner was responsible for the bite mark on Walker's neck. Petitioner's trial counsel called its own dental expert who criticized aspects of Dr. Hutson's analysis and opined that the bite mark found on Walker's neck was not distinctive enough to conclude that it came from Petitioner.”).
However, some federal courts have expressed concerns about the overall reliability of the field. Compare Burke v. Town of Walpole, 2004 WL 502617 (D. Mass. 2004), fn. 23, aff'd in part, vacated in part, 405 F.3d 66 (1st Cir. 2005) (in a civil rights case, court noted that counsel for plaintiff-defendant “off-handedly, and without citation to any meaningful authority, simply argued that bite mark evidence is but ‘junk science.’ That view, however, is not shared by any others who should know, so far as this court can determine. To the contrary, some thirty jurisdictions (and there may be more, but simply not reported), including the Commonwealth of Massachusetts, have concluded that, far from being the ‘junk science’ that counsel now suggests, bite mark evidence is relevant, reliable, and admissible.”) (emphasis in original) with Ege v. Yukins, 380 F. Supp. 2d 852 (E.D. Mich. 2005), aff'd in part, rev'd in part on other grounds, 485 F.3d 364 (6th Cir. 2007) (in a habeas petition case, reviewing court found that defense counsel in state trial was deficient for failing to object to expert testimony regarding bite marks and the high statistical probability that the marks were made by the defendant, noting that “bite mark identification evidence is much less scientifically reliable than many other types of physical or scientific evidence,” and therefore “it is difficult to conceive of a reason for not objecting to the bite mark evidence and the statistical opinion”).
Acquiring a Sample for Comparison
Absent the defendant’s consent, a nontestimonial identification order (or search warrant, if the defendant is in custody) should be used to collect a sample from the defendant (through photos, casts, or impressions) for comparison to other evidence in the case. For more information, see the related entry Nontestimonial Identification Orders.