A Murder in Lululemon… and How Blood Pattern Analysis Solved It

One morning in 2011, in Maryland, USA, an employee of the upscale yoga store Lululemon arrived at work to find a horrific crime scene.

Store worker Jayna Murray was found lying dead in a pool of blood, and her colleague Brittany Norwood was found tied up in the bathroom.

Brittany told police of two masked intruders, and police found men’s size 14 sneaker prints in the blood.

It was a case that would take many twists and turns, and finally end in a first degree murder charge.

Welcome to CS-Science. Today we are taking a look at blood pattern analysis, a forensic technique that was crucial in solving the Lululemon murder.

The TV show Dexter is where many people first saw this kind of forensic technique. The main character, Dexter Morgan, is a “blood spatter analyst” for the Miami-Metro Police Department.

But do forensic scientists really analyse blood like this? Do they really use a whole lot of red wool?

This IS a real job! But in real life it is called Blood Pattern Analysis (BPA), rather than “blood spatter analysis” as used in Dexter.

So how does this technique work?

Blood tends to travel in spherical drops because of surface tension, similar to water.

And these drops behave in a predictable manner whether they are hitting a solid surface or another liquid. In this example we see what happens when blood drips into a pre-existing pool of blood.

Blood obeys the same laws of gravity, physics and chemistry that govern all fluids.

But in most crime scenes where violent acts have taken place, blood is not just dripping freely. Blood is often travelling in a certain direction, either coming from a person’s body as the result of a forceful injury, or being flung off a moving object with blood on it, such as a weapon.

The shape and orientation of blood patterns can tell forensic scientists about the direction the blood came from. This video shows the pattern blood makes when it hits a surface at a 45o angle. The length and width of the blood pattern can be used to calculate the angle of impact, using trigonometry.

And THIS is how Dexter Morgan works out where to put his red wool, to show the path the blood has travelled and to work out the position and movements of the victim and the assailant.

Blood pattern analysis can also potentially tell us many more things about a crime:
Type of weapon
Type of injuries
Number of blows
Order of injuries
How long ago it happened
Whether death was immediate or delayed

In fact, if a forensic scientist has a theory about what happened at a crime scene, it can be tested in the lab by acting it out, seeing what the blood pattern looks like, and comparing it back to the crime scene.

The test might involve seeing how blood is flung off a bloody weapon as it is used to strike someone – this is called a Cast Off Pattern – or it might involve something bizarre, like seeing what happens when blood is dropped into coffee creamer.

TV shows like Dexter make blood pattern analysis seem straightforward and definitive but in real life, it can be complicated by a number of factors
Multiple victims?
Multiple perpetrators?
Overlapping blood patterns
Complicated cast-off
etc.

So much so that the National Research Council of the US described blood pattern analysis as having “enormous uncertainties”.

But now back to the Lululemon murder, where blood pattern analysis did tell a convincing story.

Do you remember those size 14 shoe prints that were found in the blood? They were found to have been made using a shoe that was for sale in the store.

When confronted with this evidence, Brittany admitted that she herself had killed Jayna, made the footprints in the blood, and tied herself up in the bathroom. But she said it was all an accident, that during an argument, in the heat of the moment, she hit Jayna with a clothing rail, a weapon that was located at the scene.

However, the blood pattern evidence showed that another five different weapons were used to injure and kill Jayna, all objects that were found around the store.

A blood trail showed that Jayna had tried and failed to escape, and blood was also found on the underside of a bookcase – blood that could have only got there if she was beaten while already lying on the ground. So Brittany’s story about hitting Jayna - just once - in the heat of the moment just didn’t add up.

The blood pattern evidence was crucial in proving that this was first degree murder, and Brittany was sentenced to life in prison.

And the motive?

Jayna had confronted Brittany after seeing her put a pair of yoga pants into her bag in an attempt to steal them.

Sounds like Brittany really lost her yoga zen.

That is all from CS-Science today. But if you would like to see more slow motion blood pattern analysis videos, a huge selection is available online from the Midwest Forensic Research Centre. The link is the notes.

I look forward to seeing you next time for an exciting episode on forensic entomology (that’s right, insects!). Until then!