Forensic Sci Med Pathol (2014) 10:654–661 DOI 10.1007/s12024-014-9618-8
LESSONS FROM THE MUSEUM
Use of 3D surface scanning to match facial shapes against altered exhumed remains in a context of forensic individual identification Philippe Charlier • Philippe Froesch • Isabelle Huynh-Charlier • Aure´lie Fort Agathe Hurel • Franz Jullien
•
Accepted: 22 September 2014 / Published online: 19 October 2014 Ó Springer Science+Business Media New York 2014
Objective
Materials and methods
3D surface scanning has been successfully used in forensic medicine and pathology for over a decade. We report a new application area: a technique of skull-face superimposition as a 3D-surface-scan based identification method. Our aim was to test this technology—previously used in industrial and anthropological areas—for facial proportionality evaluation and comparing a number of morphological features of the face and skull.
This study is based on a 3D correlation of skull/face of two named individuals: Henri IV and Marie-Antoine Careˆme. The head of the French King Henri IV (1553–1610) has been identified according to 22 forensic and historical arguments [1, 2] (Fig. 1a), and is waiting to be buried for the last time in the Saint-Denis Cathedral (France). A mortuary mask was made at the time of his death in 1610, and copies were displayed in anthropological and scientific institutions after the spread of phrenology [3]; the studied cast (Fig. 1b) is held in the National Museum of Natural History, Paris (MNHN-HA-5499, Gall collection). The skull and mortuary mask of Marie-Antoine Careˆme (1784–1833), a nineteenth century French paˆtissier (he served as a chef de cuisine to Talleyrand, Napole´on, Tsar Alexander I, and banker James Mayer Rothschild, and is considered to be the first internationally renowned celebrity chef, and the creator of the standard chef’s hat, the toque) [4, 5] are conserved in the National Museum of Natural History, Paris (Fig. 2a, b). Both have been part of the Dumoutier phrenologist collection since its origins (MNHN-HA-D-368, mortuary mask/MNHN-HA-29888 skull). The head of Henri IV was scanned using a medical CTscanning device for conservation reasons and because of accessibility of the material (see below for details). Both the facial mask and the skull of Careˆme have been scanned using a RANGE7 KONICA MINOLTAÒ, i.e., a non-contact 3D digitalizer developed to scan various industrial parts, including press parts, machined parts, prototypes, cast parts, and injection molded parts, to generate 3D data. Captured data can be displayed on a computer and compared with 3D CAD models (which requires optional software) to quickly output measurement reports on overall
P. Charlier (&) P. Froesch A. Hurel Section of Medical and Forensic Anthropology (UVSQ/AP-HP), UFR of Health Sciences, 2 Avenue de la Source de la Bie`vre, 78180 Montigny-le-Bretonneux, France e-mail: [email protected] P. Charlier National Museum of Natural History (MNHN), Paris, France P. Froesch GROB (Osteography Research Group), Autonomous University of Barcelona, Barcelona, Spain I. Huynh-Charlier Department of Radiology, University Hospital Pitie´-Salpeˆtrie`re (AP-HP), 45-83 Hospital Boulevard, 75013 Paris, France A. Fort Direction of Anthropological Collections, National Museum of Natural History (MNHN), 43 rue Buffon, 75005 Paris, France F. Jullien Atelier moulage et restauration, Direction des Collections, Muse´um National d’Histoire Naturelle, case postale 22, 75231 Paris Cedex 05, France
123
Forensic Sci Med Pathol (2014) 10:654–661
655
Fig. 1 Mummified head (a) and facial mask (b) of the French King Henri IV
Fig. 2 Skull (ÓJean-Christophe Domenech) (a) and facial mask (b) of Careˆme
deviation, cross-sectional deviation, wall thickness distribution, and GD&T (Geometric Dimensioning and Tolerance). The digitalization took place in the Surfac¸us structure (http://surfacus.mnhn.fr/), which main objective is to allow 3D scanning of natural science specimens, in order to improve the development and conservation of the National Museum of Natural History collections (Paris, France). The
technical capabilities of the equipment allow scanning of specimens of varying sizes (from 1 cm to several tens of centimeters) and various solid objects, or fossil bones and teeth, minerals, meteorites, etc. However, it is not possible to scan mounted specimens with hair, feathers or with transparencies. The equipment of the platform includes the RANGE7 KONICA MINOLTAÒ scanner (specifications are given in
123
656
Forensic Sci Med Pathol (2014) 10:654–661
Table 1 Specifications of the RANGE7 KONICA MINOLTAÒ Measurement method
Triangulation method of severing light
Light source
Diode laser, wavelength: 660 nm
Laser class
Class 2 (IEC 60825-1 Edition 2)
Number of pixels of the sensor
1.31 megapixels (1,280 9 1,024)
Measuring distance
450–800 mm
Receiving lens (interchangeable)
TELE, WIDE
Measuring range (mm)
450 to 800 mm, X 9 Y 79 9 99 141 9 176 150 9 188 267 9 334 Z 54 97109194
Measurement interval in the direction XY
0.08 0.14 0.16 0.28
Accuracy (distance between spheres)
40 Microns
Accuracy (Z, sigma)
4 Microns
Table 1), a stand of measures, a turntable, a tripod assembly for moving an extramural scanner, a laptop with software acquisition and data processing abilities, and a Rapidform RangeViewerÒ. The RANGE7 KONICA MINOLTAÒ performs triangulation, using a class 2 laser semiconductor for scanning the target with the laser light. In about 2 s, the target is scanned by the laser through a slit, and the reflected light is
received by the 1.31-megapixel CMOS sensor that generates high resolution data. This data is then converted into 3D data on the principle of triangulation target. Scanning provides approximately 1,310,000 dots (1,280 9 1,024 points) that serve as 3D coordinates. All data from the National Museum of Natural History have been imported in .obj format in the Zbrush 3D package (PixologicÒ USA) to superimpose the two models in Visualforensic studio in Barcelona. In Henri IV’s case, the original mummified head underwent a multidetector row computed tomography (PhilipsÒ, iCT 256) at the Pitie´-Salpeˆtrie`re Hospital (Paris, France), using the following parameters: detector configuration: 64 9 0.625 mm; slice thickness: 0.80 mm; tube voltage: 120 kV; dose per section: 601 mAs; and a final DLP of 2,303 mGy 9 cm. The .dicom database was imported in Osirix Dicom viewer (PixmeoÒ Geneva, Switzerland) and exported in .obj format to Visualforensic studio. We applied a mass displacement compensation for Henri IV’s (1553–1610) death mask, due to facial deformation which was caused by the casting being carried out with the body in a supine position, which pushes the exocanthion up and outwards, and the inferior face volume back around 5° from columnela (Fig. 3); such a scanning was done holding the device by hand. As the 1610s casting was done with plaster, we may assume that the weight and pressure of the medium was between 1 and 2 kg (mix = 1
Fig. 3 Displacement of the lips and chin is about 5° under natural gravity (vertical position). A plaster cast done in decubitus should create stronger deformations due to the mass of the mixed media and time of exposure, i.e., pressure (red = seated; gray = decubitus)
123
Forensic Sci Med Pathol (2014) 10:654–661
657
Fig. 4 Superimposed scanned volumes of three individuals in seated and decubitus positions. Differences in soft tissues mass distribution is clearly visible in two tones
Fig. 5 Superimposed scanned volumes of two individuals in seated (left) and decubitus (right) positions: exocanthions move laterally and up, so as brow lines; the mouth widens and moves back; the nasogenial and double chin soften
weight water ?1.3 weight plaster) all over the face for at least 15 min, pushing the cheeks, eyelids, and mouth up and inward in a more dramatic way (Figs. 4, 5).
Results Identification of both individuals was originally based on the evaluation of facial proportionality, and comparison of a number of morphological features of the face and skull. The most recent forensic publications dealing with skull-photo superimposition methods integrate the use of computer technology [6] that allows the professional to quantitatively assess the fit between a skull and a facial photograph in two or, ideally, three dimensions. But, one of the main pitfalls is proper sizing of the photograph and positioning of the skull. A scale correlation may be established using anatomical landmarks
such as anterior dentition or measurements of interpupillary distance [7]. Using professional image computer programs, the 3D skull image is sized so that it can be superimposed on the 3D image of the face. Once the skull and face are satisfactorily adjusted for size and basic orientation, using a list of 8 key skeletal and soft tissues landmarks (Table 2), the cranio-facial proportions in the skull and the face are evaluated and compared. We then used the Austin-Smith and Maples [8] list of morphological requirements for establishing a consistent fit between the face and the skull (a direct extrapolation from their photography/video superimposition methods for identifying unknown human skulls). Observing Marie-Antoine Careˆme’s (1784–1833) bust cast superimposed on his skull, it is possible to see that the external topography of the face smoothly matches the underlying bone structure (Figs. 6, 7).
123
658
Forensic Sci Med Pathol (2014) 10:654–661
Fig. 6 Bone and soft tissue superimposition for Careˆme’s skull and facial mask
Table 2 List of seven skeletal and soft tissues key landmarks and their corresponding soft tissue landmarks used for skull-face adjustment Skeletal landmarks
Soft tissues landmarks
Supraglabella
Supraglabella
Glabella
Glabella
Supraorbitale
Supraorbitale
Ektoconchion
Exocanthion
Anterior lacrimal crest
Endocanthion
A-point
Subnasale
Zygomatic arch midway
Zygion
Despite any soft tissue distortion, both of the skulls identities (Careˆme and Henri IV: Fig. 8) are confirmed using an infinity of points (the 12 Austin-Smith and Maples points, and the 3D curvature of the accessible skull vault, brow ridges, glabella morphology). Discussion There is a range of possible applications for 3D matching: landmark placement details, quantitative derivations,
123
statistical methods, distribution of attributes in the population, etc. Several methods for computer-assisted personality identification from the skull have been described: one based on the POSKID 1.1 software for evaluating the spatial position of the head on the portrait and adequate orientation of the skull in space with the coordination of 49 anatomical points [9]; evidence of crucial anatomical signs [10]; superposition of a three-dimensional skull surface and a two-dimensional digitized facial photograph [11]; videoskull superimposition [12]; use of photographic transparencies and drawings in a identikit-type system [13]. Our method is the only one that allows comparison of lines and curvatures, such as the forehead and other vault sections, in all the dimensions of space, considerably improving the reliability/accuracy of the identification process. Using discrete landmarks always results in a finite amount of points. Using modeled curves always results in a trade-off between model complexity and match error between curve and actual data. Either way, these technical intricacies are a necessary aspect of proper surface modeling in the 3D match/comparison setting. Another limitation could be that using manually placed landmarks is not precise, and could even be less accurate
Forensic Sci Med Pathol (2014) 10:654–661
659
Fig. 7 Skeletal and soft tissue landmarks for Careˆme’s skull and facial mask
on 3D models than on 2D models. Defining the exact placement process for landmarks, averaging placement results from several users, and then possibly blinding landmark placement if done manually, may be of key importance to later matching coordinates in match sets compared to non-match sets. But then, matching coordinates across different scans or modalities is statistically difficult: indeed, what test would we use? How to account for errors? Are some landmarks harder to get right than others and how to account for them? The use of lines and curvatures, that include a very large number of points and landmarks, is a way of testing and validating the method, and excluding these potential biases. Usually, quantifying a match against a non-match involves creation of some type of data space first, and to calibrate that, one usually requires some known matches, against which then the questionable matches are compared. This could be a second method of 3D landmark comparison that we have not carried out here.
Conclusion 3D surface scanning is of high interest for forensic purposes, as it allows direct morphological and measurement comparison of the skull and face. Identification can be the result of either the exclusion of the skull as a match to the face, or the failure to exclude the skull as a match to the face. In this case, both identities of the skulls were confirmed using an infinity of points (the 12 Austin-Smith and Maples points, and 3D curvature of the accessible skull vault). Our method avoids any complications that may be caused by using photographs (such as focal length, overexposure or underexposure, and out-of-focus distortions), and problems with skull/photograph scaling and alignment. All data are numerically correlated. Finally, this method allows comparison of not only a dozen anatomical points, but an infinity of points (using lines and curvatures, such as the forehead and other vault sections, in all the dimensions
123
660 Fig. 8 Superimposition of hard (bone) and soft tissues before (left) and after (right) correction of facial volume for Henri IV’s skull and facial mask
123
Forensic Sci Med Pathol (2014) 10:654–661
Forensic Sci Med Pathol (2014) 10:654–661
of space), that considerably improves the reliability/accuracy of the identification process. Acknowledgments To He´le`ne Rossinot and Camilla Staunton, for their professional English proofreading. To Alain Froment and Philippe Mennecier, for the full access to the anthropological collection of the MNHN, Paris. To both anonymous reviewers for their contribution in the improvement of this research.
References 1. Charlier P, Huynh-Charlier I, Poupon J, Keyser C, Lancelot E, Favier D, et al. Multidisciplinary medical identification of a French King’s head (Henri IV). BMJ. 2010;341:c6805. 2. Charlier P, Lalueza-Fox C, Herve´ C. The head of Henri IV: identification and ethical issues. Rev Prat. 2013;63(2):289–93. 3. Livianos-Aldana L, Rojo-Moreno L, Sierra-Sanmiguel PFJ. Gall and the phrenological movement. Am J Psychiatr. 2007;164(3): 414. 4. Kelly I. Cooking for Kings. The life of Antonin Careˆme, the first celebrity chef. London: Walker & Company; 2003. 5. Charlier P. Death of a pastry chef. Br Dent J. 2013;215:155.
661 6. Delfino VP, Colonna M, Vacca E, Potente F, Introna F. Computer-aided skull-face superimposition. Am J Forensic Med Pathol. 1986;7(3):201–12. 7. Loh FC, Chao TC. Skull and photographic superimposition: a new approach using a second party’s interpupil distance to extrapolate the magnification factor. J Forensic Sci. 1989;34(3):708–13. 8. Austin-Smith D, Maples WR. The reliability of skull/photograph superimposition in individual identification. J Forensic Sci. 1994;39:446–55. 9. Zviagin VN, Ivanov NV, Narina NV. Computer-aided personality identification by skull and life-time photography by POSKID 1.1 method. Sud Med Ekspert. 2000;43(5):22–9. 10. Fitsezheva NV. Possibilities of craniofacial identification from incomplete and damaged skulls. Sud Med Ekspert. 2008;51(3): 15–7. 11. Nickerson BA, Fitzhorn PA, Koch SK, Charney M. A methodology for near-optimal computational superimposition of twodimensional digital facial photographs and three-dimensional cranial meshes. J Forensic Sci. 1991;36(2):480–500. 12. Fenton TW, Heard AN, Sauer NJ. Skull-photo superimposition and border deaths: identification through exclusion and the failure to exclude. J Forensic Sci. 2008;53(1):34–40. 13. Aulsebrook WA, Iscan MY, Slabbert JH, Becker P. Superimposition and reconstruction in forensic facial identification: a survey. Forensic Sci Int. 1995;75(2–3):101–20.
123
LESSONS FROM THE MUSEUM
Use of 3D surface scanning to match facial shapes against altered exhumed remains in a context of forensic individual identification Philippe Charlier • Philippe Froesch • Isabelle Huynh-Charlier • Aure´lie Fort Agathe Hurel • Franz Jullien
•
Accepted: 22 September 2014 / Published online: 19 October 2014 Ó Springer Science+Business Media New York 2014
Objective
Materials and methods
3D surface scanning has been successfully used in forensic medicine and pathology for over a decade. We report a new application area: a technique of skull-face superimposition as a 3D-surface-scan based identification method. Our aim was to test this technology—previously used in industrial and anthropological areas—for facial proportionality evaluation and comparing a number of morphological features of the face and skull.
This study is based on a 3D correlation of skull/face of two named individuals: Henri IV and Marie-Antoine Careˆme. The head of the French King Henri IV (1553–1610) has been identified according to 22 forensic and historical arguments [1, 2] (Fig. 1a), and is waiting to be buried for the last time in the Saint-Denis Cathedral (France). A mortuary mask was made at the time of his death in 1610, and copies were displayed in anthropological and scientific institutions after the spread of phrenology [3]; the studied cast (Fig. 1b) is held in the National Museum of Natural History, Paris (MNHN-HA-5499, Gall collection). The skull and mortuary mask of Marie-Antoine Careˆme (1784–1833), a nineteenth century French paˆtissier (he served as a chef de cuisine to Talleyrand, Napole´on, Tsar Alexander I, and banker James Mayer Rothschild, and is considered to be the first internationally renowned celebrity chef, and the creator of the standard chef’s hat, the toque) [4, 5] are conserved in the National Museum of Natural History, Paris (Fig. 2a, b). Both have been part of the Dumoutier phrenologist collection since its origins (MNHN-HA-D-368, mortuary mask/MNHN-HA-29888 skull). The head of Henri IV was scanned using a medical CTscanning device for conservation reasons and because of accessibility of the material (see below for details). Both the facial mask and the skull of Careˆme have been scanned using a RANGE7 KONICA MINOLTAÒ, i.e., a non-contact 3D digitalizer developed to scan various industrial parts, including press parts, machined parts, prototypes, cast parts, and injection molded parts, to generate 3D data. Captured data can be displayed on a computer and compared with 3D CAD models (which requires optional software) to quickly output measurement reports on overall
P. Charlier (&) P. Froesch A. Hurel Section of Medical and Forensic Anthropology (UVSQ/AP-HP), UFR of Health Sciences, 2 Avenue de la Source de la Bie`vre, 78180 Montigny-le-Bretonneux, France e-mail: [email protected] P. Charlier National Museum of Natural History (MNHN), Paris, France P. Froesch GROB (Osteography Research Group), Autonomous University of Barcelona, Barcelona, Spain I. Huynh-Charlier Department of Radiology, University Hospital Pitie´-Salpeˆtrie`re (AP-HP), 45-83 Hospital Boulevard, 75013 Paris, France A. Fort Direction of Anthropological Collections, National Museum of Natural History (MNHN), 43 rue Buffon, 75005 Paris, France F. Jullien Atelier moulage et restauration, Direction des Collections, Muse´um National d’Histoire Naturelle, case postale 22, 75231 Paris Cedex 05, France
123
Forensic Sci Med Pathol (2014) 10:654–661
655
Fig. 1 Mummified head (a) and facial mask (b) of the French King Henri IV
Fig. 2 Skull (ÓJean-Christophe Domenech) (a) and facial mask (b) of Careˆme
deviation, cross-sectional deviation, wall thickness distribution, and GD&T (Geometric Dimensioning and Tolerance). The digitalization took place in the Surfac¸us structure (http://surfacus.mnhn.fr/), which main objective is to allow 3D scanning of natural science specimens, in order to improve the development and conservation of the National Museum of Natural History collections (Paris, France). The
technical capabilities of the equipment allow scanning of specimens of varying sizes (from 1 cm to several tens of centimeters) and various solid objects, or fossil bones and teeth, minerals, meteorites, etc. However, it is not possible to scan mounted specimens with hair, feathers or with transparencies. The equipment of the platform includes the RANGE7 KONICA MINOLTAÒ scanner (specifications are given in
123
656
Forensic Sci Med Pathol (2014) 10:654–661
Table 1 Specifications of the RANGE7 KONICA MINOLTAÒ Measurement method
Triangulation method of severing light
Light source
Diode laser, wavelength: 660 nm
Laser class
Class 2 (IEC 60825-1 Edition 2)
Number of pixels of the sensor
1.31 megapixels (1,280 9 1,024)
Measuring distance
450–800 mm
Receiving lens (interchangeable)
TELE, WIDE
Measuring range (mm)
450 to 800 mm, X 9 Y 79 9 99 141 9 176 150 9 188 267 9 334 Z 54 97109194
Measurement interval in the direction XY
0.08 0.14 0.16 0.28
Accuracy (distance between spheres)
40 Microns
Accuracy (Z, sigma)
4 Microns
Table 1), a stand of measures, a turntable, a tripod assembly for moving an extramural scanner, a laptop with software acquisition and data processing abilities, and a Rapidform RangeViewerÒ. The RANGE7 KONICA MINOLTAÒ performs triangulation, using a class 2 laser semiconductor for scanning the target with the laser light. In about 2 s, the target is scanned by the laser through a slit, and the reflected light is
received by the 1.31-megapixel CMOS sensor that generates high resolution data. This data is then converted into 3D data on the principle of triangulation target. Scanning provides approximately 1,310,000 dots (1,280 9 1,024 points) that serve as 3D coordinates. All data from the National Museum of Natural History have been imported in .obj format in the Zbrush 3D package (PixologicÒ USA) to superimpose the two models in Visualforensic studio in Barcelona. In Henri IV’s case, the original mummified head underwent a multidetector row computed tomography (PhilipsÒ, iCT 256) at the Pitie´-Salpeˆtrie`re Hospital (Paris, France), using the following parameters: detector configuration: 64 9 0.625 mm; slice thickness: 0.80 mm; tube voltage: 120 kV; dose per section: 601 mAs; and a final DLP of 2,303 mGy 9 cm. The .dicom database was imported in Osirix Dicom viewer (PixmeoÒ Geneva, Switzerland) and exported in .obj format to Visualforensic studio. We applied a mass displacement compensation for Henri IV’s (1553–1610) death mask, due to facial deformation which was caused by the casting being carried out with the body in a supine position, which pushes the exocanthion up and outwards, and the inferior face volume back around 5° from columnela (Fig. 3); such a scanning was done holding the device by hand. As the 1610s casting was done with plaster, we may assume that the weight and pressure of the medium was between 1 and 2 kg (mix = 1
Fig. 3 Displacement of the lips and chin is about 5° under natural gravity (vertical position). A plaster cast done in decubitus should create stronger deformations due to the mass of the mixed media and time of exposure, i.e., pressure (red = seated; gray = decubitus)
123
Forensic Sci Med Pathol (2014) 10:654–661
657
Fig. 4 Superimposed scanned volumes of three individuals in seated and decubitus positions. Differences in soft tissues mass distribution is clearly visible in two tones
Fig. 5 Superimposed scanned volumes of two individuals in seated (left) and decubitus (right) positions: exocanthions move laterally and up, so as brow lines; the mouth widens and moves back; the nasogenial and double chin soften
weight water ?1.3 weight plaster) all over the face for at least 15 min, pushing the cheeks, eyelids, and mouth up and inward in a more dramatic way (Figs. 4, 5).
Results Identification of both individuals was originally based on the evaluation of facial proportionality, and comparison of a number of morphological features of the face and skull. The most recent forensic publications dealing with skull-photo superimposition methods integrate the use of computer technology [6] that allows the professional to quantitatively assess the fit between a skull and a facial photograph in two or, ideally, three dimensions. But, one of the main pitfalls is proper sizing of the photograph and positioning of the skull. A scale correlation may be established using anatomical landmarks
such as anterior dentition or measurements of interpupillary distance [7]. Using professional image computer programs, the 3D skull image is sized so that it can be superimposed on the 3D image of the face. Once the skull and face are satisfactorily adjusted for size and basic orientation, using a list of 8 key skeletal and soft tissues landmarks (Table 2), the cranio-facial proportions in the skull and the face are evaluated and compared. We then used the Austin-Smith and Maples [8] list of morphological requirements for establishing a consistent fit between the face and the skull (a direct extrapolation from their photography/video superimposition methods for identifying unknown human skulls). Observing Marie-Antoine Careˆme’s (1784–1833) bust cast superimposed on his skull, it is possible to see that the external topography of the face smoothly matches the underlying bone structure (Figs. 6, 7).
123
658
Forensic Sci Med Pathol (2014) 10:654–661
Fig. 6 Bone and soft tissue superimposition for Careˆme’s skull and facial mask
Table 2 List of seven skeletal and soft tissues key landmarks and their corresponding soft tissue landmarks used for skull-face adjustment Skeletal landmarks
Soft tissues landmarks
Supraglabella
Supraglabella
Glabella
Glabella
Supraorbitale
Supraorbitale
Ektoconchion
Exocanthion
Anterior lacrimal crest
Endocanthion
A-point
Subnasale
Zygomatic arch midway
Zygion
Despite any soft tissue distortion, both of the skulls identities (Careˆme and Henri IV: Fig. 8) are confirmed using an infinity of points (the 12 Austin-Smith and Maples points, and the 3D curvature of the accessible skull vault, brow ridges, glabella morphology). Discussion There is a range of possible applications for 3D matching: landmark placement details, quantitative derivations,
123
statistical methods, distribution of attributes in the population, etc. Several methods for computer-assisted personality identification from the skull have been described: one based on the POSKID 1.1 software for evaluating the spatial position of the head on the portrait and adequate orientation of the skull in space with the coordination of 49 anatomical points [9]; evidence of crucial anatomical signs [10]; superposition of a three-dimensional skull surface and a two-dimensional digitized facial photograph [11]; videoskull superimposition [12]; use of photographic transparencies and drawings in a identikit-type system [13]. Our method is the only one that allows comparison of lines and curvatures, such as the forehead and other vault sections, in all the dimensions of space, considerably improving the reliability/accuracy of the identification process. Using discrete landmarks always results in a finite amount of points. Using modeled curves always results in a trade-off between model complexity and match error between curve and actual data. Either way, these technical intricacies are a necessary aspect of proper surface modeling in the 3D match/comparison setting. Another limitation could be that using manually placed landmarks is not precise, and could even be less accurate
Forensic Sci Med Pathol (2014) 10:654–661
659
Fig. 7 Skeletal and soft tissue landmarks for Careˆme’s skull and facial mask
on 3D models than on 2D models. Defining the exact placement process for landmarks, averaging placement results from several users, and then possibly blinding landmark placement if done manually, may be of key importance to later matching coordinates in match sets compared to non-match sets. But then, matching coordinates across different scans or modalities is statistically difficult: indeed, what test would we use? How to account for errors? Are some landmarks harder to get right than others and how to account for them? The use of lines and curvatures, that include a very large number of points and landmarks, is a way of testing and validating the method, and excluding these potential biases. Usually, quantifying a match against a non-match involves creation of some type of data space first, and to calibrate that, one usually requires some known matches, against which then the questionable matches are compared. This could be a second method of 3D landmark comparison that we have not carried out here.
Conclusion 3D surface scanning is of high interest for forensic purposes, as it allows direct morphological and measurement comparison of the skull and face. Identification can be the result of either the exclusion of the skull as a match to the face, or the failure to exclude the skull as a match to the face. In this case, both identities of the skulls were confirmed using an infinity of points (the 12 Austin-Smith and Maples points, and 3D curvature of the accessible skull vault). Our method avoids any complications that may be caused by using photographs (such as focal length, overexposure or underexposure, and out-of-focus distortions), and problems with skull/photograph scaling and alignment. All data are numerically correlated. Finally, this method allows comparison of not only a dozen anatomical points, but an infinity of points (using lines and curvatures, such as the forehead and other vault sections, in all the dimensions
123
660 Fig. 8 Superimposition of hard (bone) and soft tissues before (left) and after (right) correction of facial volume for Henri IV’s skull and facial mask
123
Forensic Sci Med Pathol (2014) 10:654–661
Forensic Sci Med Pathol (2014) 10:654–661
of space), that considerably improves the reliability/accuracy of the identification process. Acknowledgments To He´le`ne Rossinot and Camilla Staunton, for their professional English proofreading. To Alain Froment and Philippe Mennecier, for the full access to the anthropological collection of the MNHN, Paris. To both anonymous reviewers for their contribution in the improvement of this research.
References 1. Charlier P, Huynh-Charlier I, Poupon J, Keyser C, Lancelot E, Favier D, et al. Multidisciplinary medical identification of a French King’s head (Henri IV). BMJ. 2010;341:c6805. 2. Charlier P, Lalueza-Fox C, Herve´ C. The head of Henri IV: identification and ethical issues. Rev Prat. 2013;63(2):289–93. 3. Livianos-Aldana L, Rojo-Moreno L, Sierra-Sanmiguel PFJ. Gall and the phrenological movement. Am J Psychiatr. 2007;164(3): 414. 4. Kelly I. Cooking for Kings. The life of Antonin Careˆme, the first celebrity chef. London: Walker & Company; 2003. 5. Charlier P. Death of a pastry chef. Br Dent J. 2013;215:155.
661 6. Delfino VP, Colonna M, Vacca E, Potente F, Introna F. Computer-aided skull-face superimposition. Am J Forensic Med Pathol. 1986;7(3):201–12. 7. Loh FC, Chao TC. Skull and photographic superimposition: a new approach using a second party’s interpupil distance to extrapolate the magnification factor. J Forensic Sci. 1989;34(3):708–13. 8. Austin-Smith D, Maples WR. The reliability of skull/photograph superimposition in individual identification. J Forensic Sci. 1994;39:446–55. 9. Zviagin VN, Ivanov NV, Narina NV. Computer-aided personality identification by skull and life-time photography by POSKID 1.1 method. Sud Med Ekspert. 2000;43(5):22–9. 10. Fitsezheva NV. Possibilities of craniofacial identification from incomplete and damaged skulls. Sud Med Ekspert. 2008;51(3): 15–7. 11. Nickerson BA, Fitzhorn PA, Koch SK, Charney M. A methodology for near-optimal computational superimposition of twodimensional digital facial photographs and three-dimensional cranial meshes. J Forensic Sci. 1991;36(2):480–500. 12. Fenton TW, Heard AN, Sauer NJ. Skull-photo superimposition and border deaths: identification through exclusion and the failure to exclude. J Forensic Sci. 2008;53(1):34–40. 13. Aulsebrook WA, Iscan MY, Slabbert JH, Becker P. Superimposition and reconstruction in forensic facial identification: a survey. Forensic Sci Int. 1995;75(2–3):101–20.
123
