76 > forensic case

Forensic dentistry case book 6:

A self-inflicted bite mark; a case report
SADJ March 2016, Vol 71 no 2 p76 - p77

S Maistry1, V M Phillips2

CASE REPORT
The case presented is of a 35 year old woman who was ACRONYM
a victim of a vicious assault. At autopsy there were 26 ABFO: American Board of Forensic Odontology
stab wounds to the body, numerous defence injuries, her
throat was slit and there was generalised organ pallor as The analysis of the bite mark continued with the comparison
a result of exsanguination. The stab wounds fractured the of the victim’s teeth with the bite mark. Dental impressions
cervical spine and injured the lungs, oesophagus, trachea of the victim’s teeth were taken using President® silicone
as well as the arteries and veins of the neck. On the left impression material. From these dental impressions upper
arm were superficial lesions consistent with a bite mark and lower plaster of Paris study models were cast of
(Figure 1). The bite mark was photographed and swabbed the teeth for comparison purposes. These were used to
for DNA. An impression of the bite mark was not taken duplicate the biting patterns of the upper and lower teeth
because the lesions were very superficial and there was of the victim by pressing the teeth of the study models into
little penetration of the skin. softened grey dental bite-registration wax. This resulted
in an accurate bite pattern for the upper and lower teeth
The examination of the victim’s mouth showed a small red
which was then compared with the actual bite mark. The
abrasion present on the upper lip near the right corner of the
patterns of the teeth in the wax are traced onto plastic foil
mouth (Figure 2). This abrasion was adjacent to the upper
with a permanent marking pen and then super-imposed
right canine, and was possibly caused by forceful pressure
over the bite mark to elicit concordant features (Figure 3).
of the lip against the underlying canine. There was also an
abrasion of the upper lip below the left nostril; that possibly The illustrations in Figure 3 demonstrate the relationship
occurred during the attack on the victim. Examination of between the victim’s upper teeth and the bite mark on the left
the teeth of the victim showed no abnormalities. arm. The dental arch matched the outer pattern of bruises.
The bite mark on the arm showed that there were two The lower illustration shows the tracing of the biting pattern
distinct curved patterns of lesions (Figure 1) indicating that of the victim’s upper teeth superimposed on the photograph
there were two bite marks in this area. of the bite mark. Six concordant features were identified.
Photographs were taken of the bite marks using an ABFO
No. 2 mm scale (American Board of Forensic Odontology)
RESULTS
to reference the size of the lesions produced by the teeth The analysis of the bite marks in comparison with the
that had caused the pattern of bruises and abrasions. For teeth of the victim showed the following:
analytical purposes the photographs were printed to the • Six concordant features between the upper teeth and
original size of the bite marks on the arm; i.e. 1:1 ratio. the upper outer aspect of the bite mark
• Seven concordant features between the upper teeth
When a bite mark occurs on the lower arm it is important and the upper inner aspect of the bite mark
to consider self-infliction as a possibility. The arm or hand • Ten concordant features between the lower teeth and
is often forced into the victim’s mouth to minimize minimise the lower area of the bite mark.
screaming. In this case, when the left arm was placed
adjacent to the mouth it showed that there was a distinct DISCUSSION
possibility that the victim had bitten her own arm. At this IForensic pathologists need to be aware at autopsy that
stage of the investigation no suspect had been arrested. bruises and abrasions could possibly be a bite mark.1 There
are several important lessons from this case study.
1. Sairita Maistry: BSc; BSc Hons; MBCHB, Dip For. Med (SA); FC For.
Path (SA); MMED For. Path (UCT). Department of Forensic Medicine Firstly, the time lapse between the infliction of a bite mark
and Toxicology. University of Cape Town. and when it is examined is critical.2-4 If a bite mark is
2. Vincent Michael Phillips: BDS; MChD; Dip. Max-Facial Radiol; FC analysed soon after the event the chances of making an
Path SA (Oral Path); PhD; D.Sc. Department of Forensic Medicine and accurate match with the perpetrator’s, or in this case, the
Toxicology. University of Cape Town. victim’s, teeth, are greatly improved. Secondly the skin and
Corresponding author underlying tissues of the forearm are relatively soft and
Vincent Michael Phillips: malleable and allow a degree of distortion when bitten.
Department of Oral and Maxillofacial Pathology & Forensic Sciences. Therefore the abrasions and bruises may be somewhat
Faculty of Health Sciences, University of the Western Cape. South Africa. mis-shaped when compared with the teeth and the biting
Tel: 021 937 3161. E-mail: vmphillips@uwc.ac.za
patterns of whoever inflicted the bite.5,6
www.sada.co.za / SADJ Vol 71 No. 2
forensic case <
77

Figure 1: The oval pattern of the bite marks on the left arm showing two bite mark patterns Figure 2: The victim showing the lesion in the right
(ABFO mm scale). corner of the mouth and below the left nostril.

The ideal analysis of a bite mark is to take an impression of the puncture wounds
and to cast a model; this creates an accurate replica of the bite mark which can be
compared with the perpetrator’s teeth. In this case the bruises and abrasions on
the arm were too superficial to justify an impression.

Photographs of the bite marks need to be printed to as close to the original size of
the bite mark seen on the victim i.e. 1:1 ratio for accurate analysis. In this case, the
clinical and photographic examination showed distinct crescent shaped patterns
of bruises and abrasions on the skin, caused by the upper and lower teeth. The
bite marks were on the inner aspect of the left forearm of the victim. This suggested
that there was a distinct possibility that the arm of the victim was forced into her
mouth during the attack and that the bite mark was self-inflicted.10-12

The arms are usually raised during an attack with the outer surface towards the
attacker, therefore a bite inflicted by the attacker would be on the outer surface of
the arm.7,8 The abrasion and bruise patterns also suggest a struggle because there
were abrasions on the skin produced by the upper teeth that appear to have been
dragged across the skin surface due to the victim trying to remove her arm from
her mouth. The right corner of the victim’s mouth shows a lesion on the upper lip
that may have been caused by the victim’s right canine during forceful insertion of
her left forearm into her mouth. The bite marks in this victim were mostly abrasions
with no puncture wounds, further supporting self-infliction.12 A bite mark by an
attacker is usually more severe with bleeding puncture wounds.8,13

There is no consensus as to the minimum number of concordant features in bite

mark analysis which are necessary to determine a complete match between the
teeth of the perpetrator (or victim) and a bite mark.9 The greater the number of
concordant features, the higher the probability of a match. Hence in this case the
probability that the victim bit her own arm is high.13

Conclusion
Bite marks are frequently encountered by Forensic Pathologists at autopsy.
However, analysis of a bite mark requires the expertise of a Forensic Odontologist.
Figure 3: These illustrations demonstrate the
relationship between the victim’s upper teeth
This case report has demonstrated the methods used to analyse a bite mark
and the bite mark on the left arm. The lower and the need for Forensic Pathologists to be aware of bite marks and to take
illustration shows the tracing of the biting pattern DNA swabs before the autopsy. The number of concordant features in this case
of the victim’s upper teeth superimposed on suggested that there was a high degree of probability that the bite mark on the
the photograph of the bite mark, identifying six
concordant features (white arrows). left forearm of the victim was self-inflicted.

References 1983; 28 (1): 61-9.

1. Saukko P, Knight B. Knight’s Forensic Pathology. 3rd Ed. 8. Petty IA and Sweet D. Anatomical location of bitemarks and
Hodder Arnold. 2004; Chap. 26 pg.527-41 associated findings in 101 cases from the United States.
2. Thompson, I.O.C., Phillips, V.M. Bite mark case with a twist. The Journal of Forensic Sciences. 2000;45 (4): 812-4.
Journal of Forensic Odonto-Stomatology. 1994; 12: 37-40. 9. Bowers CM and Pretty IA. Expert disagreement in bite mark
3. Lessig R, Wenzel V, Weber M. Bite mark analysis in forensic casework. Journal of Forensic Sciences. 2009; 54 (4): 915-8.
routine case work. EXCLI Journal. 2006; 5: 93-102. 10. Sobel MN and Perper JA. Self-inflicted bite mark on the breast
4. Dorian RBJ. Human Bite marks in: Bite-mark Evidence: A of a suicide victim. American Journal of Forensic Medicine and
Colour Atlas and Text, 2nd Ed. Florida: CRC press. 2011; Pathology.1985; 6 (4): 336-8.
Ch.18, pg. 269-70. 11. Warnick AJ, Biedrzycki L, Russanow G. Not all bite marks are
5. Sheasby DR & MacDonald DGA. Forensic classification of associated with abuse, sexual activities, or homicides: a case
distortion of human bite marks. Forensic Science International. study of a self-inflicted bite mark. Journal of Forensic Sciences.
2001; 122 (1): 75-8. 1987; 32 (3): 788-92.
6. DeVore DT. Bite marks for identification? A preliminary report. 12. Ronchese, F. Self-inflicted bite mark. American Journal of
Medicine Science and Law.1971; 11 (3): 144-5. Surgery. 1994; 6 (1): 80-5.
7. Vale GL and Noguchi TT. Anatomical distribution of human bite 13. Furness J. A general review of bite mark evidence. American
marks in a series of 67 cases. Journal of Forensic Sciences. Journal of Forensic Medicine and Pathology.1981; 2 (1): 49-52.