#ForensicFactFriday - Blood Pattern Analysis
Published on 26 October 2018
We are launching our new #Forensicfactfriday social media series with a Halloween special.
We are launching our new #Forensicfactfriday social media series with a Halloween special. Here’s the lowdown on one of the more gruesome areas, Blood Pattern Analysis, also known as BPA, bloodstain pattern, blood spatter or splatter analysis.
We’ve also included a tried and tested recipe for creating fake blood that has a realistic consistency so you can make your own and try your own experiment and analysis. Let us know if you’ve tried it out on Twitter or Facebook.
What is it all about?
Blood pattern analysis is the study and analysis of bloodstains at crime scenes. The analysis of the blood stains attempts to recreate the actions that caused the patterns that can be seen including the size, distribution and location of the bloodstains. The distribution of blood can help investigators determine whether a violent assault was created by a gunshot wound, stabbing or other trauma.
The method was developed in 1895 by Dr Eduard Piotrowski of the University of Kraków who published a paper titled "On the formation, form, direction, and spreading of blood stains after blunt trauma to the head” but the first legal case where blood pattern analysis was used as evidence wasn’t until the 1950s in the USA. It takes time before new forensic techniques can be established as reliable and robust enough to be used within the courtroom.
On 4 July, 1954 Marilyn Sheppard was murdered in the bedroom of her home. She had more than 20 injuries to her face and scalp, blood around her body, and staining the bedsheets and pillow. Blood spots were also visible on the wall and closet doors.
Her husband, Sam Sheppard was also in the house at the time, he told a story of battling with the killer who he described as ‘bushy haired’. At the crime scene a lot of blood was found but the only blood found on Dr Sheppard was on one knee.
As the investigation was conducted on the assumption that the crime was a domestic homicide, there was reduced effort put in recovering fingerprint/blood evidence than might be expected.
Sam was arrested for the murder of his wife and found guilty of the crime at trial which opened on the 18 October 1954.
One month after Sam Sheppard’s conviction, on the 22 January 1955, Professor Paul Kirk of UC Berkeley visited the bedroom where Marilyn Sheppard had been killed. As a result of his examination, he undertook a series of experiments and wrote an extensive report on the blood patterns visible, he concluded that (published by the Cleveland State University Insitutional Repository):
- The murderer was left handed (Dr Sheppard was right handed).
- The injuries to the victim’s teeth indicated that the victim had bitten her attacker’s hand.
- A large bloodstain on the closet door was likely form the attacker’s bloody hand and testing confirmed that it did not match either the victim or Dr Sheppard, therefore there was a third person present.
- The murder weapon was a cylindrical object, such as a pip or flashlight, not a surgical instrument, as asserted by the coroner.
A request for an appeal in 1955 was not allowed, but in mid-July 1964 Federal Judge Carl Weinman overturned the conviction on federal due process grounds and on the 24 October 1966 a second trial was started. Whilst a BPA expert testified at the trial that a couple of blood spots that had been found on the rim of Dr Sheppard’s watch could only have come about if Dr Sheppard had attacked his wife, Professor Kirk gave evidence for the defence, testifying to his findings listed above. On 16 November 1966, Dr Sam Sheppard was acquitted.
There continues to be disagreement about what happened at the Sheppard house in 1954, but the use of BPA evidence in 1966 ensured that Dr Sheppard was acquitted. Since then the use of BPA evidence has become more common within criminal cases.
Although some aspects of blood pattern analysis are supported by scientific study, it was highlighted in the ‘Strengthening Forensic Science in the United States: A Path Forward’ published by the National Academy of Sciences in 2009 that experts can extrapolate the causes of patterns beyond what can be supported through research. There is still lots of research to be carried out in this area and the Leverhulme Research Centre for Forensic Science is partnering with the University of Edinburgh to address some of these areas.
Try it for yourself
Create your fake blood
Blood is not like water, it is a non-Newtonian fluid which means its viscosity changes depending on how much stress is placed on it. When blood isn’t in the body, it travels as a ball and there’s a relationship between the size of the ball and the force that created it.
This recipe, from a research study comparing blood substitutes to the real thing, creates a realistic blood consistency with which you can try your own blood pattern experiments.
- water 90ml
- scarlet food colouring (supercook) 2ml
- strawberry delight dessert mix (birds) 5g
- mix well and store at room temperature
Blood Spatter Experiment
You will need:
- fake blood
- paper (white smooth)
- chopping board
- some old clothing or carpet
- measuring tape
- a spoon (for dropping the blood)
- a ruler
- Drop blood from the same height on the different surfaces (paper, cardboard, chopping board, clothing/carpet).
- Take a photo of each spot of blood.
- Measure the size of the droplet with the ruler.
- Repeat each droplet three times.
- Change the height from which you make the drop, repeat on each surface three times.
Are there any differences between the sizes of the droplets?
Are the edges the same on all the surfaces?
Are the drops you have made on the same surface consistent?
Read the research
- National Research Council, National Academy of Sciences. 2009. Strengthening Forensic Science in the United States: A Path Forward. Washington, D.C.: National Academies Press.
- Millington J - Hull. 2004. Development of a synthetic blood substitute for use in forensic science teaching. Physical Sciences.
- The Sam Sheppard Case files available at Engaged Scholarship Digital Repository at Cleveland State University.
- On the formation, form, direction, and spreading of blood stains after blunt trauma to the head, (Eduard Piotrowski, Ueber Entstehung, Form, Richtung und Ausbreitung der Blutspuren nach Hiebwunden des Kopfes) Vienna, Austria: 1895