Skip to main content
SpringerLink
Log in

Experimental measurement of breath exit velocity and expirated bloodstain patterns produced under different exhalation mechanisms

  • Original Article
  • Published:
International Journal of Legal Medicine Aims and scope Submit manuscript

Abstract

In an attempt to obtain a deeper understanding of the factors which determine the characteristics of expirated bloodstain patterns, the mechanism of formation of airborne droplets was studied. Hot wire anemometry measured air velocity, 25 mm from the lips, for 31 individuals spitting, coughing and blowing. Expirated stains were produced by the same mechanisms performed by one individual with different volumes of a synthetic blood substitute in their mouth. The atomization of the liquid at the lips was captured with high-speed video, and the resulting stain patterns were captured on paper targets. Peak air velocities varied for blowing (6 to 64 m/s), spitting (1 to 64 m/s) and coughing (1 to 47 m/s), with mean values of 12 m/s (blowing), 7 m/s (spitting) and 4 m/s (coughing). There was a large (55–65%) variation between individuals in air velocity produced, as well as variation between trials for a single individual (25–35%). Spitting and blowing involved similar lip shapes. Blowing had a longer duration of airflow, though it is not the duration but the peak velocity at the beginning of the air motion which appears to control the atomization of blood in the mouth and thus stain formation. Spitting could project quantities of drops at least 1600 mm. Coughing had a shorter range of near 500 mm, with a few droplets travelling further. All mechanisms could spread drops over an angle >45°. Spitting was the most effective for projecting drops of blood from the mouth, due to its combination of chest motion and mouth shape producing strong air velocities. No unique method was found of inferring the physical action (spitting, coughing or blowing) from characteristics of the pattern, except possibly distance travelled. Diameter range in expirated bloodstains varied from very small (<1 mm) in a dense formation to several millimetres. No unique method was found of discriminating expirated patterns from gunshot or impact patterns on stain shape alone. Only 20% of the expirated patterns produced in this study contained identifiable bubble rings or beaded stains.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13
Fig. 14

Similar content being viewed by others

References

  1. State, vs. Peterson (2013) Court of Appeals of North Carolina, No. COA12–1047

  2. Scientific Working Group on Bloodstain Pattern Analysis (SWGSTAIN) (2009) Scientific Working Group on Bloodstain Pattern Analysis: Recommended Terminology. Forensic Science Communications 11(2). The Federal Bureau of Investigation Laboratory Division. https://archives.fbi.gov/archives/about-us/lab/forensic-science-communications/fsc/april2009/standards/2009_04_standards01.htm. Accessed 15 Nov 2016

  3. Donaldson AE, Taylor MC, Cordiner SJ, Lamont IL (2010) Using oral microbial DNA analysis to identify expirated bloodspatter. Int J Legal Med 124(6):569–576

    Article  PubMed  Google Scholar 

  4. Emes A (2001) Expirated blood: a review. J Can Soc Forensic Sci 34(4):197–203

    Article  Google Scholar 

  5. Donaldson AE, Walker NK, Lamont IL, Cordiner SJ, Taylor MC (2011) Characterising the dynamics of expirated bloodstain pattern formation using high-speed digital video imaging. Int J Legal Med 125(6):757–762. doi:10.1007/s00414-010-0498-5

    Article  PubMed  Google Scholar 

  6. Chao CYH, Wan MP, Morawska L, Johnson GR, Ristovski ZD, Hargreaves M, Mengersen K, Corbett S, Li Y, Xie X, Katoshevski D (2009) Characterization of expiration air jets and droplet size distributions immediately at the mouth opening. J Aerosol Sci 40(2):122–133. doi:10.1016/j.jaerosci.2008.10.003

    Article  CAS  Google Scholar 

  7. Yang S, Lee GWM, Chen C-M, Wu C-C, Yu K-P (2007) The size and concentration of droplets generated by coughing in human subjects. Journal of Aerosol Medicine 20(4):484–494. doi:10.1089/jam.2007.0610

    Article  PubMed  Google Scholar 

  8. Denison D, Porter A, Mills M, Schroter RC (2011) Forensic implications of respiratory derived blood spatter distributions. Forensic Sci Int 204(1–3):144–155. doi:10.1016/j.forsciint.2010.05.017

    Article  PubMed  Google Scholar 

  9. Carter GS (1996) A consideration of coughed and spat-out blood. Forensic Science Service Report No TN 817, August 1996

  10. Geoghegan PH, Spence CJT, Wilhelm J, Kabaliuk N, Taylor MC, Jermy MC (2016) Experimental and computational investigation of the trajectories of blood drops ejected from the nose. Int J Legal Med 130(2):563–568. doi:10.1007/s00414-015-1163-9

    Article  CAS  PubMed  Google Scholar 

  11. Geoghegan PH, Spence CJT, Kabaliuk N, Wilhelm J, Aplin J, Taylor MC, Jermy MC (2014) The flow field external to the human nose and the acceleration of blood drops from the nasal cavity during violent assault. In: 17th International Symposium of Laser Techniques to Fluid Mechanics, Lisbon, Portugal, 7th–10th July. http://ltces.dem.ist.utl.pt/lxlaser/lxlaser2014/finalworks2014/papers/03.15_1_108paper.pdf. Accessed 15 Nov 2016

  12. Bond NI (2008) Validation of assumptions underlying the angle of impact calculation for a bloodstain and the development of a synthetic blood substitute. Dissertation, University of Auckland, Auckland, New Zealand

Download references

Acknowledgements

We would like to thank Margaret Dodds for her patient help with the experimental set-up and obtaining materials.

Author information

Authors and Affiliations

  1. Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, Canterbury, 8041, New Zealand

    P.H. Geoghegan & M.C. Jermy

  2. University of Applied Sciences Van Hall Larenstein, Leeuwarden, 8934 CJ, The Netherlands

    A.M. Laffra & N.K. Hoogendorp

  3. Christchurch Science Centre, Institute of Environmental Science and Research (ESR), 27 Creyke Road, Christchurch, Canterbury, 8041, New Zealand

    M.C. Taylor

Authors
  1. P.H. Geoghegan
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. A.M. Laffra
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. N.K. Hoogendorp
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. M.C. Taylor
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. M.C. Jermy
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to P.H. Geoghegan.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Geoghegan, P., Laffra, A., Hoogendorp, N. et al. Experimental measurement of breath exit velocity and expirated bloodstain patterns produced under different exhalation mechanisms. Int J Legal Med 131, 1193–1201 (2017). https://doi.org/10.1007/s00414-017-1545-2

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00414-017-1545-2

Keywords

Search

Navigation