Facial soft tissue thickness and facial recognition in black South African adults
Date
2019
Authors
Meiring, Keegan O
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Abstract
Forensic facial approximations are used when conventional methods of identification provide
insufficient results. The success of these facial approximations are founded on access to the
applicable facial soft tissue thicknesses (FSTT), the culmination of muscle and connective
tissue extending the distance from the outer surface of the bone to the external extreme of the
skin. The aims of this study were to supplement existing South African FSTT data and
investigate their reliability by utilizing facial recognition tests.
Sixty computed tomography (CT) scans were obtained retrospectively from the Wits Donald
Gordon Medical Centre (Johannesburg) after obtaining ethical clearance. On each scan,
FSTTs were measured at 10 midline and 10 bilateral landmarks. South African sex-specific &
pooled data, as well as FSTT from the C-Table repository (available through
http://www.CRANIOFACIALidentification.com) were utilized to perform several facial
approximations using the Manchester method. Assessors were then asked to study the facial
arrays and indicate which photographs of the 20 presented to them resembled the facial
approximations.
The FSTT measurements were collected for 47 females (78.3%) and 13 males (21.7%). The
range of the midline and lateral means were 2.4 to 11.3 mm and 6.5 to 29.8 mm respectively.
The range of the midline and lateral shorths were 1.8 to 10.4 mm and 5.6 to 27.5 mm
respectively. Moreover, the 75-shormaxes of midline and lateral landmarks ranged from 3.3
to 13.2 mm and from 8.4 to 37.6 mm respectively. Statistical significance between sexes for
FSTT, was found to only exist at the mid-zygomatic landmark (t-test; p<0.05). One
significant difference was accounted for at the supra M2 pertaining to bilateral asymmetry.
Age-related differences, mostly in the vicinity of the eyes and nose, were however,
statistically significant at several midline and bilateral landmarks. The facial approximations
produced in this study displayed subtle changes depending on the data used to achieve them
(i.e.: sex-specific or pooled data). Variations in the appearance of the jaw line, parotid region
and mouth were the most noticeable; however, these did not influence recognisability. All
categories of assessors exhibited above-chance success during the facial array tests. The
female approximations were paired with correct photograph 30% more frequently than the
male approximations; however, the difference was not statistically significant. White females
with experience of anatomy and/or art displayed the highest success during the facial arrays
and indicated that the bridge of the nose and breadth of the nostrils were the most telling
features.
The results of this study have uncovered that the categorization of FSTTs does not
significantly influence the recognition rates of facial approximation. Facial approximations
produced using pooled data were identified more easily.
Furthermore, recognition biases associated with sex and ancestry were not significant in the
current South African study.
Description
A dissertation submitted to the School of Anatomical Sciences, Faculty of Health Science,
The University of the Witwatersrand, South Africa, in fulfillment of the requirements for the
degree Master of Science in Medicine
Johannesburg, South Africa
March, 2019
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Citation
Meiring, Keegan Oliver (2019) Facial soft tissue thickness and facial recognition of black South African adults, University of the Witwatersrand, Johannesburg, <http://hdl.handle.net/10539/28050>