Browsing by Author "Steyn, Maryna"

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Development of the Wits Face Database: an African database of high-resolution facial photographs and multimodal closedcircuit television (CCTV) recordings [version 1; peer review: 2 approved]
(2021) Bacci, Nicholas; Davimes, Joshua; Steyn, Maryna; Briers, Nanette
Forensic facial comparison is a commonly used, yet under-evaluated method employed in medicolegal contexts across the world. Testing the accuracy and reliability of facial comparisons requires large scale controlled and matching facial image databases. Databases that contain images of individuals on closed-circuit television (CCTV), with matching formal and informal photographs are needed for this type of research. Although many databases are available, the majority if not all are developed in order to improve facial recognition and face detection algorithms through machine learning, with very limited if any measure of standardisation. This paper aims to review the available databases and describe the development of a high resolution, standardised facial photograph and CCTV recording database of male Africans. The database is composed of a total of 6220 standardised and uncontrolled suboptimal facial photographs of 622 matching individuals in five different views, as well as corresponding CCTV footage of 334 individuals recorded under different realistic conditions. A detailed description of the composition and acquisition process of the database as well as its subdivisions and possible uses are provided. The challenges and limitations of developing this database are also highlighted, particularly with regard to obtaining CCTV video recordings and ethics for a database of faces. The application process to access the database is also briefly described.
Forensic facial comparison: current status, limitations, and future directions.
(MDPI, 2021-12-03) Bacci, Nicholas; Davimes, Joshua G.; Steyn, Maryna; Briers, Nanette
Global escalation of crime has necessitated the use of digital imagery to aid the identification of perpetrators. Forensic facial comparison (FFC) is increasingly employed, often relying on poorquality images. In the absence of standardized criteria, especially in terms of video recordings, verification of the methodology is needed. This paper addresses aspects of FFC, discussing relevant terminology, investigating the validity and reliability of the FISWG morphological feature list using a new South African database, and advising on standards for CCTV equipment. Suboptimal conditions, including poor resolution, unfavorable angle of incidence, color, and lighting, affected the accuracy of FFC. Morphological analysis of photographs, standard CCTV, and eye-level CCTV showed improved performance in a strict iteration analysis, but not when using analogue CCTV images. Therefore, both strict and lenient iterations should be conducted, but FFC must be abandoned when a strict iteration performs worse than a lenient one. This threshold ought to be applied to the specific CCTV equipment to determine its utility. Chance-corrected accuracy was the most representative measure of accuracy, as opposed to the commonly used hit rate. While the use of automated systems is increasing, trained human observer-based morphological analysis, using the FISWG feature list and an Analysis, Comparison, Evaluation, and Verification (ACE-V) approach, should be the primary method of facial comparison.
Wits Face Database
(2020-11-02) Bacci, Nicholas; Davimes, Joshua; Steyn, Maryna; Briers, Nanette; Data Manager: N Bacci,
The human face is important in social, cultural and recognition contexts. Many research fields make use of faces to understand human interaction and identify individuals. Studies relying on facial image data often make use of ad hoc datasets specifically created for those studies as there is a dearth of large scale controlled and matching facial image databases. Actualistic (taken in a real life, natural setting) and standardised databases of facial images can be of extreme value to many research areas, such as facial identification and recognition. While multiple face databases are available, the majority, if not all, are developed in order to address very specific questions and hypotheses with limited standardisation, severely limiting their potential applicability. The Wits Face Database was developed as a generic, yet actualistic dataset of facial images obtained from consenting young adult South African male individuals. This database consists of high resolution standardised facial photographs (3264 x 4080 pixels) and corresponding closed-circuit television (CCTV) recordings of male South Africans under different camera conditions. A total of 6220 standardised (clothing and background controlled) and natural (visible clothing and out of focus background) facial photographs of 622 matching individuals in five different views are included. Corresponding CCTV footage of 334 of these individuals is also included. Across both the CCTV recordings and the photographs, the faces were captured in five different views: anterior, left 45-degree, left lateral, right 45-degree, and right lateral. The CCTV recordings were grouped under the following actualistic conditions: a standard internet protocol (IP) CCTV set-up, a low-resolution analogue CCTV set-up, an eye-level IP CCTV system, and the standard IP CCTV set-up with the addition of sunglasses and caps for target individuals. A detailed description of the composition and acquisition process of the database will be made available in a database descriptor publication format. The database is available strictly for non-commercial scientific research following approval of a formal application, assessed by the School of Anatomical Sciences’ Collections Committee within the University of the Witwatersrand.