Expirated blood – How the research began and where it is today

Billie-Jo Jenkins, 13, was murdered on February 15th 1997[1] after being hit in the head several times with an iron tent peg. Billie-Jo’s foster father, Siôn Jenkins, was convicted of her murder in July 1998. The evidence used to convict Siôn was the presence of many small blood drops on his clothing (72 on his jacket, 76 on his trousers and 10 on his left shoe).[2] There was a lot of ambiguity over how the blood got on to Siôn’s clothing. It was suggested during his trial that the blood had been expirated by Billie-Jo. Expirated blood implies that the person was still able to breathe when the blood was transferred to the object. In this case, that definition would mean that Siôn was with Billie-Jo when she was still alive. Some experts believed that this was not possible due to the wounding present on Billie-Jo’s head, which was severe enough to cause almost immediate death. It has been suggested that the blood could have originated from the attack itself, being a medium to high velocity impact attack. At the time of this case, there was very little research that had been performed on expirated blood, so both prosecution and defence needed to come up with plausible explanations, along with supporting research, as to how the blood got there. In February 2006, Siôn Jenkins was acquitted of the murder of Billie-Jo after serving 6 years in prison for the crime. Publicity surrounding the case is still rife, although no one has been convicted at present.

It was only after this case that forensic scientists realised that there was a distinct lack of research surrounding the analysis of expirated blood patterns. The problem with this was that, as shown in the case study above, it can lead to difficulties solving crimes since there is a gap in research to support a legal stand point. Since then, a few pieces of research have been published, but very few focussing on the basics of visual pattern identification. There are several publications stating what the characteristics of expirated blood are, but there are no references or identifiable research to support these statements. Silenieks[3], Donaldson et al,[4] and Power et al[5] researched the detection of components of saliva as a marker of expirated blood patterns. However, it is only Denison et al\citeDenison2011} and Emes[6] who have recently researched and identified common physical and visual markers of expirated blood. It was the lack of recent research in this area that lead me to study this further as part of my undergraduate degree.

One of the questions that this researched aimed to answer was, “What are the defining characteristics of expirated blood patterns that make differentiation from high velocity impact patterns easier? Do these characteristics match those of previous research?”

Blood patterns are a collection of blood droplets within relatively close proximity which commonly show directionality,[7] approximate the velocity of impact, and determine the area of origin (although sometimes few or none of these are present). Due to the amount of information blood patterns can provide, it is important that they are analysed accurately and with confidence. Expirated blood is defined as blood that has been forced out through the mouth, nose, a neck wound, or any in which air is the main propellant.[6]

The method for generating expirated blood patterns using a human participant was to measure 2cm3 of a blood substitute using a graduated plastic pipette and to then squeeze this ‘blood’ into the mouth. This was then coughed at A3 paper from distances of 50cm or 1m and from angles of 45o or 90o. The paper was labelled with the test number, volume of blood used, distance, and angle of impact before being left to dry, ready for analysis.

Expirated beading

Once dried, the blood patterns were inspected to identify any droplets that contained characteristics of expirated blood, as identified by previous research. By creating expirated blood patterns using a human participant, it was possible to identify the defining characteristics of expirated blood that make it easier to differentiate from high velocity impact patterns. The characteristics identified during this research match the characteristics identified by Clark,[8] Denison et al,[9] Emes,[6] MacDonell,[10] James,[11] and Donaldson et al.[12] These characteristics are listed below:

  • Diluted stains with a mottled effect (where blood has mixed with saliva)
  • Irregular shape (stains commonly are not rounded in shape and have uneven edges)
  • Irregular size (patterns can have various sized stains, ranging from low- to high-velocity impacts in the same pattern)
  • Beading (where the blood has not had the chance to separate into individual droplets: a string of blood connects several droplets, as shown in the accompanying image
  • Bubble voids (where the blood has been introduced to the airways and a bubble has formed, leaving a void in the centre of a stain where the bubble was before it popped. This void should have little or no blood in it and should be rounded in shape)

Carrying on from the previously mentioned research, it would be of interest to see further research in the comparison of expirated blood patterns with other, similar blood patterns, such as those created via insect activity at a crime scene. It is important to advance the knowledge of the blood patterns analysis area in order to ensure that patterns identified in cases are as accurately identified as possible, and to correctly identify their method of creation. In order to do this, it is essential to perform more research into differentiating similar types of blood patterns, as seen within this paper. Further work could include the analysis of a larger sample of blood patterns to ensure that statistic tests performed provided valid conclusions.


  1. L. Smith, Jenkins had blood on clothes, court told, The Guardian, 22 April 2005.
  2. The Facts of the Case, Accessed 5th April 2013.
  3. E. Silenieks, The detection of salivary amylase in expirated blood patterns, I.A.B.P.A News June, pp. 5–7, 2006.
  4. A.E. Donaldon, M.C. Taylor, S.J. Cordiner & I.L. Lamont, Using oral microbial DNA analysis to identify expirated bloodspatter, International Journal of Legal Medicine 124, pp. 569–576, 2010.
  5. D.A. Power, S.J. Cordiner, J.A. Kiester, G.R. Tompkins & J. Horswell, PCR-based detection of salivary bacteria as a marker of expirated blood, Science & Justice 50, p. 59, 2010.
  6. A. Emes, Expirated blood - A review, Journal of the Canadian Society of Forensic Science 34(4), pp. 197–203, 2001.
  7. A.R.W. Jackson & J.M. Jackson, 'Bloodstain Pattern Analysis' in Forensic Science, Pearson Education Limited, Gosport, 2008.
  8. K. Clark, Differentiating high velocity blood spatter patterns, expirated bloodstains, and insect activity, I.A.B.P.A News September, 2006.
  9. D. Denison, A. Porter, M. Mills & R.C. Schroter, Forensic implications of respiratory derived blood spatter distributions, Forensic Science International 204, pp. 144–155, 2011.
  10. H.L. MacDonell, Crime scene evidence - blood spatters and smears and other physical evidence, Quinnipiac Health Law Journal 1, pp. 33–45, 1996.
  11. Reference not found.
  12. A.E. Donaldson, N.K. Walker, I.L. Lamont, S.J. Cordiner & M.C. Taylor, Characterising the dynamics of expirated bloodstain pattern formation using high-speed digital video imaging, International Journal of Legal Medicine 125, pp. 757–762, 2011.