Craniofacial superimposition | Photographic, Video and Roentgenographic Superimposition

FORENSIC SCIENCEFORENSIC ANTHROPOLOGY

Shubham Kumar

1/29/20244 min read

Craniofacial Superimposition refers to the techniques exclusively used in forensic anthropology, in order to contribute evidential value in the personal identification process under investigation. In this system, the image of the skull is overlayed onto the image of the missing person's face.

This technique is very difficult to administer and require a very high perception and technical skills in order to obtain the maximum results. Craniofacial superimposition is usually come in action when no other method left to foster the identification process under investigation.

This technique is used when no other means of information is available and is based on the assumptions that the skull can be of that person whom police is searching. The assumptions lands on the dynamics of relevance in shape and size of the skull and image of the missing person's face.

Methods of Craniofacial Superimposition

The techniques called craniofacial superimposition can deliver action via, 3 methods. Photographic method, Video method and Roentgenographic Superimposition.

Photographic Superimposition

The photographic superimposition is the primary method in craniofacial superimposition. This method is used when the difference between the image of skull and the image of missing person is not much. In these techniques, the image of skull is overlayed onto the image of the missing person. This can be executed either by the computer or manually by hand. The superimposition, of the images take place on the same scale. After alignment in the scale parameter, the features of the skull and the image of missing person is then matched.

  • Advantages- This technique is non-invasive in nature and is relative ease of use.

  • Disadvantages- This technique requires high quality and pixels photographs. Moreover, may encounter errors due to variations in angles and positioning between the skull and the photography.

Different Approaches:

1. Direct Superimposition: This method directly overlays a photograph of a suspect or victim onto a photograph of a skull or face. It's most effective when features are clear and there is a high degree of similarity between the two images.

2. Indirect Superimposition: Here, a photograph of a suspect or victim is used to create a plaster or clay model of their face. This model is then overlaid onto a photograph of a skull or face for comparison. It's useful when the original photograph is of low quality or when features aren't clearly visible.

3. Reverse Superimposition: In this technique, a photograph of a skull or face is overlaid onto a photograph of a suspect or victim. It's beneficial when the photograph of the suspect or victim is of higher quality or when there are more visible features to compare.

4. Computer-Assisted Superimposition: This advanced method utilizes computer software to overlay photographs and create composite images. It's particularly helpful in cases involving multiple suspects or victims, allowing for the comparison of multiple images simultaneously.

Video Super Imposition

Unlike photographic method, video superimposition requires less technicality and experience, as all the major part is being governed by the compute system. This method involves the analysis by the development of 3-D model of skull and the missing person, and then comparing their features by the computer system. The 3-D model is created by capturing the footage of the skull and the photograph of the missing person. After creation of the 3-D models, both the models are compared to each other in terms of features, in order to determine whether the skull belongs to this person or not.

  • Advantages: This method offers high accuracy and allows manipulation of digital models for precise feature matching.

  • Limitations: However, it requires expensive equipment and specialized software, which may not be accessible in all forensic settings.

Types of Video Superimposition
  1. Static Superimposition: Involves overlaying still images onto crime scene videos. This can be particularly useful when the video quality is poor or when the features of the individual are not clearly visible.

  2. Dynamic Superimposition: This technique overlays videos onto crime scene footage, providing a more comprehensive view of the events. It helps reconstruct the sequence of events leading up to the crime.

  3. Forensic Image Comparison: It's about comparing images or videos from different sources to identify similarities or differences. This can be crucial in comparing suspects or victims with surveillance footage or other sources.

  4. 3D Computer Modeling: Utilizes advanced computer software to create a 3D model of a crime scene or relevant footage. This provides investigators with a more complete view of the events leading up to the crime.

Roentgenographic Super Imposition

Unlike photographic and video superimposition who uses image and 3-D models for comparison, Roentgenographic superimposition technique underlines the importance of X-Ray images in forensic analysis. This technique involves the overlaying of X-Ray image of skull and mission person's face. The analysis and comparison between these X-Ray images is performed at same scale. The images are then aligned and the features of both the images are matched. The technique inherits prevalence over photographic and video method in domains like dentistry and orthopedics.

  • Advantages: Reveals internal structures and features, like dental records, not visible on the surface.

  • Limitations: However, it requires expensive equipment and specialized software, Moreover, the workers may get radioactive exposer.

Two-dimensional (2D) Superimposition
  • Involves overlaying a skull X-ray or photograph of a deceased person's skull with a 2D antemortem photograph.

  • The antemortem photograph is adjusted to match the size and orientation of the skull image, and then the two images are superimposed to check for a match.

  • Faster and less expensive than 3D superimposition but may not capture all individual facial features.

Three-dimensional (3D) Superimposition:
  • Involves overlaying a 3D skull model, created from a CT scan or MRI of the skull, with a 3D model of the face, created from an antemortem photograph or a 3D facial scan.

  • The two models are adjusted to match in size and orientation, and then the face model is superimposed onto the skull model to check for a match.

  • Provides a more detailed and accurate comparison but requires specialized equipment and expertise.

Reference

  • "Forensic DNA Typing" by John M. Butler

  • "The Forensic Casebook: The Science of Crime Scene Investigation" by Ngaire E. Genge

  • "Forensic Science: A Very Short Introduction" by Jim Fraser

  • "Practical Crime Scene Processing and Investigation" by Ross M. Gardner