A Technique to Capture, Analyze, and Quantify Anterior Teeth Rotations for Application in Court Cases Involving Tooth Marks

Oral bacterial DNA-based discrimination of human and canine saliva for the analysis of indistinct bite marks

Analyzing ambiguous bite marks using conventional morphological approaches to identify attackers is difficult; thus, applying molecular biological methods for identifying an attacker from their saliva is a possible approach in a forensic investigation. This study aimed to establish oral bacterial DNA-based human and canine saliva markers and develop a practical method for their discrimination. We considered Streptococcus oralis and Pasteurella canis as human and canine saliva marker candidates, respectively. Duplex bacterial DNA detection using melting curve analysis was designed and evaluated for forensic applicability using proof-of-concept experiments. S. oralis DNA was detected from human saliva samples from 30 out of 30 individuals, and P. canis DNA was detected from canine saliva samples from 73 out of 77 individuals (26 dog breeds). Additionally, both bacterial DNA markers were accurately detected from human blood-contaminated saliva samples and mock indistinct bite marks. Our results indicate that both bacterial DNA markers were sensitive, robust, and discriminating saliva markers. We consider that our duplex bacterial DNA examination is a simple, practical, and useful method for the detection of saliva from indistinct bite marks and discrimination between human and canine saliva.

An analysis of dental intercanine distance for use in court cases involving bite marks

High levels of crime in South Africa and the resulting court cases requiring bite mark evidence have necessitated continuous research into the prevalence and interrelationship of recognisable dental features present in bite marks. This study represents the largest data set of descriptive statistics related to intercanine distance, in which the means, standard deviations, medians and interquartile ranges across four racial groups were determined. Intercanine distances were also statistically weighted by determining the common, uncommon and very uncommon values for each of the racial groups. The results of this research show that we can consider any maxillary intercanine distance more than 24.1 mm and less than 43.0 mm to represent a human bite mark. Black males had the largest mean (average) intercanine distance of 36.33 mm (standard deviation 2.49 mm) and white females the smallest mean intercanine distance of 33.4 mm (standard deviation 2.13 mm). The analyses showed statistically significant differences between the mean intercanine distances of different race and gender groupings. The authors do not advocate trying to determine the race or gender from intercanine distances determined, but rather the relevance of the intercanine distances in the specific race and gender groupings. This study makes a meaningful scientific contribution to the presentation of bite mark evidence at a time when subjective opinions need to be replaced with scientific data.

Are they dermatological lesions, bottle top burns or bite mark injuries?

Bite marks can be considered as a patterned injury where identification of the causative tool will lead to the identification of the perpetrator. When patterned injuries resembling bite marks are seen on the victim or an assailant of a potential crime, all efforts must be made to carry out an immediate and proper investigation. The classical human bite mark pattern will appear as an oval or circular injury. However there are several dermatological lesions which can be misinterpreted or confused with bite marks. Similarly scars left as a result of contact with hot objects can sometimes bear a resemblance to bite marks. To the untrained eye, identification of bite mark injuries is not an easy task. Since bite marks are common in cases of child abuse and neglect, it is recommended that dental surgeons with forensic background become members of the child abuse and neglect management teams. During investigation of bite marks in alleged cases of child abuse and neglect, it is imperative to compare the injury with dentition of all the persons who have direct access to the child including siblings and playmates. Information revealed through the forensic analysis of bite marks not only helps in the criminal investigation but also in the clinical management of the persons concern.

Patterns of variation and match rates of the anterior biting dentition: characteristics of a database of 3D-scanned dentitions

An understanding of the variability of the anterior human dentition is essential in bitemark analysis. A collection of 1099 3D laser scans of paired maxillary and mandibular arches were studied using geometric morphometric methods. Analyses were performed without scale (shape only) and with scale (shape and size). Specimens differing by no more than experimentally obtained measurement error were counted as matches, or as indistinguishable. A total of 487 maxillary (396 size preserved), 131 mandibular (83 size preserved), and one paired dentition (two size preserved) matches were found. Principal component analysis and partial least squares revealed interpretable patterns of variation and covariation in dental shape, principally dominated by variation in dental arch width. The sensitivity of match rate to assumed degree of measurement error was also determined showing rapid increases in match rate as measurement error increased. In conclusion, the concept of dental uniqueness with regard to bitemark analysis should be approached with caution.

Reconstruction of deformed bite marks using affine transformations

Bite marks inflicted on animate and inanimate objects will undergo a certain degree of deformation. This fact remains one of the biggest stumbling blocks when analyzing evidence for court presentation. It has been demonstrated that the reliability of pattern association analysis will not be affected by minimal degrees of warping, shrinkage, and distortion. In this study, affine transformations were applied to bite marks to establish if minimal distortions would affect the mathematically determined relationships of the defined features. In a real case study, it was then tested whether the distorted bite mark matched the dentition of the perpetrator by applying an affine transformation. This was confirmed to be the case. Affine transformations will thus not affect the relationships of the individual features found in bite marks. The numerical calculations validate the reliability of pattern association analysis in the presence of minimal amounts of warping, shrinkage, and distortion.