October 2004 - Volume 6 - Number 4

Case Report

Use of Digital Imaging in the Identification of Fragmentary Human Skeletal Remains: A Case from the Republic of Panama

Ann H. Ross
Assistant Professor of Anthropology
Department of Sociology and Anthropology
North Carolina State University
Raleigh, North Carolina

Abstract | Introduction | Background | Preliminary ExaminationAnalysis
Gerardo Olivares? | Photographic Superimposition | Discussion | References

Abstract

Photographic superimposition of digital images resulted in the positive identification of a “disappeared” Chilean national found in the Republic of Panama. Comparisons of antemortem and postmortem images of fragmentary skeletal remains that had been buried since 1977 were performed using an IBM-compatible computer and Adobe Photoshop 6.0.

Introduction

Photographic superimposition is useful when the remains are likely to belong to a particular missing person, and photographs are available (Ubelaker 2000; Ubelaker et. al. 1992). Generally, this technique is best used for exclusion, but a positive identification is possible if the morphological features are unique (Ubelaker 2000).

The methods for comparison of antemortem photographs to human skeletal remains have ranged in complexity from the relatively simple approach of using photographic comparisons, to more complex use of video-mediated methods (Matsui 2001). All of these methods necessitate the use of complete skulls for comparison, which may not always be available. This case report presents the utility of using digital images in the positive identification of fragmentary skeletal remains using a method described by Matsui (2001).

Background

On November 15, 2003, the forensic anthropology team for the Panamanian Truth Commission flew by helicopter to the island of Coiba, the largest island in the Mesoamerican Pacific. The island is located 24km offshore from Panama and is separated from the mainland on the east by the Gulf of Montijo and on the northwest by the Gulf of Chiriqui. The island’s first inhabitants were indigenous groups dating to 500 BC, who were expelled from the island by Spanish conquistadors sometime in the early part of the 16th century. It was soon abandoned by the Spaniards and was only reinhabited in 1914 when it became a penitentiary, which currently holds approximately 100 inmates.

The Panamanian Truth Commission’s directive is to investigate the deaths and disappearances by the military regimes of Generals Torrijos (1968-1978) and Noriega (1983-1989). On this mission, the forensic anthropology team went to the Maranon Cemetery, which is situated at the central encampment of the penal colony, to verify information provided by informants as to the possible location of the graves of a Panamanian and a Chilean who disappeared in 1977. Because of this testimony, four burials were exhumed and their contents analyzed.

Preliminary Examination

Basic antemortem biological information was provided for both individuals. The Panamanian, Cecilio Hazlewood, was predominantly of African ancestry, whereas the Chilean, Gerardo Olivares, had typical Andean features (indigenous) and, in particular, unique nasal bone morphology. The contents of the burials were examined in situ, and two of the burials were determined to be more recent than the late 1970s due to their state of preservation. They were thus discarded as possibilities. The state of preservation of the two remaining burials was consistent with burials from the 1970s. One grave contained the remains of an individual of predominantly African ancestry consistent with the general population of Panama. However, burial T-116 contained the remains of an individual of predominantly indigenous ancestry and notably not of Central American or African origin. In addition, this individual had unique nasal bone morphology also consistent with the antemortem biological information provided for the Chilean.

Analysis

The skeletal remains from burial T-116 are in a relatively good state of preservation with some root activity, such as surface erosion and root growth around and within some of the skeletal elements. However, many of the more fragile elements composed of predominantly cancellous bone, such as vertebrae, ribs, pelvis, and long bone epiphyses, are completely fragmentary. Two shirts were bundled and placed adjacent to the skull (occipital portion) on the left side. One shirt was orange and the other was white with blue anchors. Both were 1970s-style with large, pointed collars. This individual was also wearing a pair of red trousers. Based on the condition of the remains and the style of clothing, this burial is most likely post-1970 (Figure 1).

Figure 1. Photograph of Burial T-116

Morphological characteristics of the cranium (prominent supraorbital ridges, rugose nuchal area, blunt supraorbital margins, and square chin) and metric analysis (femur midshaft diameter, Black 1978) indicate that this individual is male.

The remains represent an individual in young adulthood (20-34 years). The remains do not exhibit evidence of osteoarthritis or other degenerative changes. Based on the overall degree of skeletal degeneration, this individual is more likely in his 20s to early 30s. The fragmentary nature of the remains prevents a more precise determination of age.

Ancestry was assessed by gross cranial morphology. Craniofacial features (broad face, nasal overgrowth, projecting zygomatics, blurred nasal sill, large teeth, and edge-to-edge bite) are characteristic of an individual of indigenous ancestry, and notably not of African origin (Bass 1995; Krogman and Iscan 1986; Rhine 1990).

The maximum radial length (236mm) was used to estimate stature. Generally, upper limb bones should not be used to estimate stature as evidenced by the larger standard deviations; however, the left radius was the only complete long bone available. The predictive stature equation for Mexican males (more appropriate for an indigenous individual) derived by Trotter (1970) was used. The predicted stature is 164.5cm +/- 4.04cm with a 95 percent prediction interval of 156.4-172.6cm.

This individual exhibits unique nasal bone morphology. The nasal bones project from the skull at approximately a 90-degree angle. This individual also has a deviated nasal septum, which encroaches into the left nasal cavity.

These remains are consistent with the antemortem biological information provided for Gerardo Olivares.

Who was Gerardo Olivares?

In 1969 after Gerardo Olivares finished mandatory military enlistment in the Chilean Navy, he went to the Chiriqui region of Panama where he joined forces with, and was to become second in command of, the guerillas opposing the military regime. He was detained in 1972 and spent time in various prisons around Panama until finally being sentenced to Coiba.

Last year a letter addressed to the Head of State of the National Guard (or military junta) dated in the year 1977 was discovered. According to this letter, the detainee, Gerardo Olivares, was shot several times while attempting to escape.

Photographic Superimposition

A scanned antemortem black-and-white photograph of Gerardo Olivares and his sister was provided for comparison (Figure 2). Because the remains were interred for an extended period, the skull was fragmentary. However, some unique facial features remained intact that allowed comparisons to be made (Figures 3 and 4). The digital superimposition was performed using an IBM-compatible computer and the software, Adobe Photoshop 6.0. The postmortem images were taken in the field using a Sony Cyber-shot model DSC-F717 digital camera. An important caveat is to avoid artificial or unintentional manipulation of digital images such as stretching to resize images (Matsui 2001).

Figure 2. Original Black-and-White Photograph of Gerardo Olivares and his Sister

Figure 3. Photograph Taken in the Field of the Lateral Aspect of the Nasal Bone Illustrating the Unique Nasal Bone Morphology

Figure 4. Frontal or Anterior of the Same Cranial Fragment

First, Gerardo Olivares was cropped from the antemortem image (Figure 5). Second, the background was removed from the postmortem image in the anterior view (Figure 6). Next, the postmortem image was scaled and rotated to fit the facial angle observed in the antemortem image. Finally, the digital image of the skull was overlaid onto the antemortem image, which remained in the background. The image of the skull was then moved to properly align the anatomical structures using the “hand tool” (Figure 7).

Anatomical consistency was examined for glabella, nasal bone morphology, shape of the eye orbit, and zygomatic or cheek bone. Significant anatomical consistencies were observed in the antemortem and postmortem images, and the remains could not be ruled out as those belonging to Gerardo Olivares. In addition, the uniqueness of the nasal bone morphology and glabella are consistent with known morphological features for Olivares and are compelling enough to allow a positive identification.

Figure 5. Cropped Image of Gerardo Olivares

Figure 6. Frontal or Anterior of the Same Cranial Fragment after the Background Was “Erased” Using Photoshop

Figure 7. Superimposition or Overlay of the Skull onto the Image of Olivares Showing Anatomical Matches

Discussion

This case illustrates how modern computer imaging software can be used in the photographic superimposition of fragmentary skeletal remains. In particular, this method can be useful in cases when there are limited resources, and when more expensive and rigorous methods for positive identifications, such as mtDNA, are not a feasible option.

Acknowledgement

The author would like to thank Mr. Gary Knight, City-County Bureau of Identification, Raleigh, North Carolina, for his technical support during the initial phase of the superimposition.

References

Bass, W. M. Human Osteology: A Laboratory and Field Manual. Special Publications Missouri Archaeological Society, Columbia, Missouri, 1995.

Black, T. K. A new method for assessing sex of fragmentary skeletal remains: Femoral shaft circumference, American Journal of Physical Anthropology (1978) 78:227-231.

Krogman W. M. and Iscan, M. Y. Human Skeleton in Forensic Medicine. Thomas, Springfield, 1986.

Matsui, K. Digital imaging in forensic medicine. In: Digital Color Imaging in Biomedicine. ID Corporation, Tokyo, 2001, pp. 73-76.

Rhine, S. Non-metric skull racing. In: Skeletal Attribution of Race: Methods for Forensic Anthropology. G. W. Gill and S. Rhine, eds. Maxwell Museum of Anthropology Anthropological Papers No. 4, Albuquerque, New Mexico, 1990, pp. 9-20.

Trotter, M. Estimation of stature from intact long limb bones. In: Personal Identification in Mass Disasters. T. D. Stewart, ed. National Museum of Natural History, Washington, DC, 1970, pp. 71-83.

Ubelaker, D. H. History of Smithsonian-FBI collaboration in forensic anthropology, especially in regard to facial imagery, Forensic Science Communications [Online]. (October 2000).

Ubelaker, D. H., Bubniak, E., and O’Donnell, G. E. Computer-assisted photographic superimposition, Journal of Forensic Sciences (1992) 37(3):750-762.