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Backspatter Phenomenon IAI
20
Definition
[Forensic Science Communications April, 2009 Vol II (2)]:
Backspatter Phenomenon
A bloodstain pattern resulting from blood drops that travel in the opposite direction of the external force applied, associated with an entrance wound created by a projectile.
Description
[SWGSTAIN Atlas of BPA Patterns and Terminology, 2012]:
- Size: Diameter < 1mm up to several mm
- Shape: Circular to elliptical
- Distribution: May radiate outward from area of origin
- Miscellaneous: Generally less abundant than forward spatter - Intervening objects such as hair and clothing will affect the amount of back spatter present. - Amount and distribution dependent upon specific weapon used and wound location
Classification
Providence 8th of August
IAI, 2013 Conference
Active phenomena
Impacting mechanism
Spatters
Impact pattern
Impact pattern core
Backspatter pattern
Forward Spatter pattern
Mist pattern
Projected mechanisms
Transfer mechanisms
Aurélien Rubio
Philippe Esperança
Phenomena involved
Martin Fackler, 1992:
Boyd G. Stephens, Terence B. Allen, 1983:
"collapse of the temporary wound cavity as the probable source of most gunshot spatter, both forward or back"
"blow back effect produced by discharge of a large volume of gas in a confined space (...) The acceleration force is the backwards stream of escaping gas trapped between the elastic skin and rigid skull"
Bernd Karger & al, 1996-1997:
James O. Pex, Charles H. Vaughan, 1987:
"blow out of the skin. (...). In a minority of gunshots to the head, secondary backspatter follows primary backspatter after a short interval when a swell of blood from the wound impacts on the floor.
Backspatter of blood is produced by the subcutaneous gas pressure and additionally by intracranial overpressure and tail spalshing"
"result of kinetic energy transfer from the hot gases entering the wound after the projectile and expanding the surrounding tissues"
1
2
Results
Backspatters III
Backspatters I
Backspatters II
0.2 to 0.4 ms
16 to 28 ms
0 ms
0.3 to 0.5 ms
2 to 4 ms
Conclusion
Backspatters I
Backspatters II
Backspatters III
- Mechanical interaction bullet/tissue
- Spatters stains
- KE transfert
- Overpressure
- Stream action
- Projected stains!!
- KE transfert
- Cavitation
- Stream action
- Projected stains!!
20-30 ms
0 ms
4
Future
- Shape
- Size
- Distribution
Analysis
Training
- CSI
- BPA
Contributor
Laurent Martrille
Thank you for
your attention
Contact :
Aurélien Rubio
Philippe Esperança
aurelien.rubio@gmail.com
ph.esperanca@gmail.com
You can find this presentation at :
http://prezi.com/kftlxq46ajir/backspatter-phenomenon-iai/
State of Art
Actual french CSI documentation
Experiments
Sponge practicals
Sponge
Sig Sauer 2022
9mm
bottom side
15cm from the sponge
Human head models practicals
bullet trajectory
Substitête Model
Thali Model
Radford Model
M.J. Thali, B.P. Kneubuehl, U. Zollinger, et R. Dirnhofer.
INPS Lille, Lab. d’Anthropologie Biologique de Lille, LAMIH Valenciennes
Philippe Noirtin
Gemma Elizabeth Radford. « Modelling Cranial Gunshot Wounds and Backspatter ». Thesis, University of Otago, 2010. http://otago.ourarchive.ac.nz/handle/10523/393.
« The “skin-skull-brain model”: a new instrument for the study of gunshot effects ». Forensic Science International 125 ( 2-3), 2002: 178–189.
Spheroic model 1
Spheroic model 2
Transparent model
Silicone cap
with artificial leather fibers
« A study of the morphology of gunshot entrance wounds, in connection with their dynamic creation, utilizing the “skin-skull-brain model” ». Forensic Science International 125 (2-3), 2002: 190–194.
Hollow polyurethane sphere
with gelatine inside