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| Credit: faro.com |
Every
incident leaves traces at the scene and efficient crime scene processing is crucial
to every investigation. Correctly processed and stored documentation is necessary
for analysis, interpretation and presentation in Courts. Some evidence is more
challenging to collect and transport to forensic laboratories than other.
For example, ephemeral and transient evidence such as footprints, tool impressions and blood spatter cannot be seized in situ and maintained in its original state. Traditionally, this type of evidence was collected using photography, sketches, electrostatic lifting or casting (Komar et al, 2011). 3-D laser scanner mapping has become an integral technique used by crime scene investigators in crime scene reconstruction, thanks to its effectiveness, portability and high accuracy.
For example, ephemeral and transient evidence such as footprints, tool impressions and blood spatter cannot be seized in situ and maintained in its original state. Traditionally, this type of evidence was collected using photography, sketches, electrostatic lifting or casting (Komar et al, 2011). 3-D laser scanner mapping has become an integral technique used by crime scene investigators in crime scene reconstruction, thanks to its effectiveness, portability and high accuracy.
3-D laser
scanners are very useful in processing traffic collisions or fatal fire scenes, as burned human
remains are sensitive to any physical manipulation, and evidence of trauma can
be easily lost. Images of the scene and human remains can be captured in situ
and then transferred to forensic laboratory for further processing. 3-D images are
saved in microns – the
measurement of space. In addition, even portable laser scanners can capture
objects of any size, which is especially useful during, for example, grave processing
for evidence of tool impressions (such as shovel and other prints), where the whole
grave and its contents can be captured in a single 3-D image. Moreover, ambient
lighting does not affect the quality of images and captures crystal clear
evidence unlike a traditional photography (Komar et al, 2011).
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| Credit: faro.com |
Documentation
of crime scene is important for further analysis and presentation of
gathered evidence in Courts for precise crime scene reconstruction. 3-D laser
scanners can accurately capture millions of data points and create a 3-D point
cloud to enable virtual viewing (FARO, 2017). There is no threat of contamination
of the scene, unlike with traditional methods used by CSIs, such as tape
measuring or use of measuring wheels. The captured scene can be revisited
multiple times in a laboratory to evaluate the progress of the investigation.
In murder
investigations, a blood spatter analysis is one of the most important
techniques used to determine what happened to the victim and how. Blood spatter
on walls has to be processed in situ. This can be labour intensive and very
time consuming. By 3-D laser scanning, it can be easily captured and processed
later in a laboratory to determine where the blood source was located, probable location
of the suspect and possible number of impacts. Recent research has found that
processing time using FARO X33 3D in comparison with manual methods can
be more than halved and significantly cut labour costs (Dubyk, Liscio, 2016).
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| Credit: www.forensicmed.co.uk |
Bite marks
are present in 8 out of 10 homicide
and sexual assaults, hence precise
documentation is crucial (Evans et al, 2013).
Bite marks are unique dental imprints that can be transferred onto skin or other surfaces, leaving behind biological and physical evidence. Not all bite marks can be used as evidence though, for example, when the unique pattern is not accurately transferred onto the victim’s skin. For evidence to be admissible in court, the bite mark has to be sufficiently visible, and distinctive to identify the suspect and the images of the bite mark and suspect’s teeth dental cast must be highly accurate. Also, the dynamics of biting itself and the viscoelasticity of the skin have to be considered during analysis. In addition to mandatory DNA collection, different methods are used to compare suspect’s dentition with victim’s injury, such as ‘confocal scanning electron microscope, reflex scanning electron microscope, fingerprint dusting powder, overlays, and 3-D laser scanning of dental casts’ (Hemalatha et al, 2014). It has been argued that capturing bite mark evidence is problematic with conventional 2-D images as these cannot precisely capture 3-D structure of human body in 2-D space, and distortion often prevents such evidence to be admitted in Courts (Evans, 2013). Innovative 3-D laser scanners such as, for example, a newly developed ‘FARO Forensic ScanArm Solution’, with a resolution of 0.05 mm, can significantly reduce the distortion and provide more accurate images (FARO, 2017).
Although
3-D laser scanners proved to be extremely effective in capturing and storing various evidence,
they also have some disadvantages. Although considerably more affordable in
recent years, the high cost of scanners might not fit the budget of smaller law
enforcement units. Also, capturing reflective or metallic surfaces can be
problematic as an interference with the scanner can occur. As scanners need a power source – forensic investigators might find it difficult to use them in highly remote locations.
Regular maintenance and training are important, as incorrect use of the 3-D laser scanner can produce artifacts on the images, leading to
misinterpretations (Komar et al, 2011).
References:
Dubyk, M., Liscio, E., (2016). Using a 3D Laser Scanner to Determine the Area of Origin of an Impact Pattern. Journal of Forensic Identification, 66(3), 259-272.
Evans, S.T., Jones, C., Plassmann, P. (2013). 3D imaging for bite mark analysis. The Imaging Science Journal 61(4), 351-360. DOI: 10.1179/1743131X11Y.0000000054.
FARO (2017). Crime Scene Analysis. Retrieved from goo.gl/MPB9Bc.
Hemalatha, et al. (2014). Identification of bite mark perpetrators in forensic dentistry - A review.
Komar, D.A., Davy-Jow, S., Decker, S.J. (2011). The Use of a 3-D Laser Scanner to Document Ephemeral Evidence at Crime Scenes and Postmortem Examinations. Journal of Forensic Sciences, 57(1), 188-191. DOI: 10.1111/j.1556-4029.2011.01915.x.
Molina, A., Martin-de-las-Heras, S. (2014). Accuracy of 3D Scanners in Tooth Mark Analysis. Journal of Forensic Sciences, 60(1), 222-226. DOI: 10.1111/1556-4029.12598.
Thali
et al. (2003) Bite mark documentation and analysis: The forensic 3D/CAD
supported photogrammetry approach. Forensic Science International 135(2),
115-21. DOI: 10.1016/S0379-0738(03)00205-6.