Just call me Dexter

Time to talk about my favorite class again! Forensic Science!

The week I have been eagerly anticipating is finally here! Bloodstain Pattern Analysis.

The Dexter in me was smiling with an evil grin :)

Our class was taught by the BPA expert in Western Australia: Fiona McQuisten.

She’s been working for the police department for 18 years, and in Forensics (BPA) for 16 years. She holds the rank of Senior Sergeant, and is an ‘acting’ Inspector. (A rank slightly above Senior Sergeant)

She gave us about an hour long presentation (slide show) of different blood stains and explained the techniques that they use to analyze the blood. It seems complicated at first, but then as you go on and keep learning it really is all common sense. I won’t go into super detail but it was absolutely fascinating and amazingly simple at the same time. I am also one of the few people that read the chapter in our textbook about BPA and it was so informative and interesting!

After the crash course in identification of different blood spatter patterns and drops, she gave us a worksheet to do. We had to look at pictures and identify what type of patterns they were (arterial, wipe, swipe, pooling, etc.) and then based on the pattern and direction of the blood speculate possible scenarios about what happened. It was a fascinating exercise! (I know I keep using that word but it’s the word that keeps coming to mind!) The crash course, and then the matching/labeling activity took up the first two hours and after that Fiona told us that she had two real cases that she worked on with her, and anyone who wished to examine them could stay, but otherwise the class was dismissed.

As you can guess, nobody left. Everyone was entranced.

So Fiona presented to us two REAL cases that she worked on. She made sure first that no one in the class knew the victims, the she proceeded to explain the cases and show us the real pictures from the scene and we “worked through” the case with her, based solely on the blood evidence to figure out what happened, and then after our hypotheses she walked us through the case with the OTHER details from detectives and told us exactly what happened. IT WAS AMAZING.

Yes seeing the crime scene photos were very gory, but Fiona put black bars covering the bodies on the slides because she said it isn’t necessary to see that gore in order to learn about BPA. The only times we saw photos of the body was if it had specific information relating to the determination of what exactly happened in the crime. For example, in one of the pictures we saw the lower portion of a body (mainly the feet) because there was blood covering the tops of the feet, but not the bottom. What does this indicate? It was quite the smoking gun in the case because the attacker alleged that the victim was attacking him through multiple rooms of the house, but if that were true she would have blood on the bottoms of her feet from walking through the blood and allegedly chasing the attacker. But because she only had blood on the top of her feet, it was indicative of the victim being dragged through blood, not walking. (There was blood covering the whole house, it would be impossible to walk around and NOT get it on the bottoms of your feet).

ISN’T THAT SO COOL?!

Obviously you can tell how much I loved this week’s class, but I still don’t think BPA or any forensic science would be a good career for me. Mainly because I am not too keen on science and the mountains of paperwork you have to do, and the amount of documentation you have to do at a crime scene (video, pictures, sketches, lists, reports, etc.) Plus, if you miss a piece of evidence, or document it incorrectly, or interpret it incorrectly, it can be catastrophic and I don’t want that kind of pressure on my back! Regardless, I thoroughly enjoyed the experience that Fiona provided to us. I graciously thanked her for speaking to our class after it was over.

Here are some notes I took that I thought I’d share with you guys:

*BPA tells you HOW something happened. It can tell you about the victim, weapon, actions, severity of attack, the sequencing of multiple “bloodshed events,” positioning of persons, directionality, angle of impact, objects used, force, and if a person attempted a clean up (along with many other things)

*The absence of evidence is NOT evidence of absence.

*Hemastix are test strips used to confirm if a substance is truly blood. Nail polish, rust, paint, sauces, and other things can sometimes be mistaken for blood and hemastix can detect if it is blood or not. Hemastix can yield false positive for a number of reasons and some items that create false positives are: rust, beetroot, horseradish, copper, cabbage, bleach, and plant material. Also if the hemastix is exposed to air for too long before the test, or past its expiration date it can tamper with the validity of the test. (So many variables to consider!) (Hemastix are usually just a quick test done at the scene and much more thorough testing is done later at the lab)

*Context must always be considered when determining what the blood tells you.

*Different surfaces affect bloodstain shape/size (Think of a drop of blood hitting tile verses hitting carpet)

*In order to sequence bloodstains it is important to attend the crime scene yourself to establish context because it is very hard to speak in absolute positives when you cannot see the scene as a whole.

*Chemical detection of blood is high in sensitivity, and low in specificity.

*When speaking in legal situations and with detectives BPA experts must use terms such as “blood shed event” (stabbing, shooting, etc) “blood source” (victim) and “penetrating injuries” (stab wounds)

*If flies are present at the scene they will eat and excrete blood. (gross) In effect, “fly spots” are sometimes mistaken for blood spatter when in reality its bloody fly poop! Crazy! These things you would never think about you know?

Here are some categories of bloodstain patterns:

*Wipe

*Swipe

*Transfer/contact

*Drip

*Flow

*Pools

*Saturation stains

*Impact

*Splashes

*Cast-off

*Arterial spurt/gush

*Expirated

*Void (What the ABSENCE of blood in an area can tell you)

*Fly spot

*Bubble rings

*Perimeter/skeletonized

Hope this didn’t upset you guys and you weren’t eating lunch or something! Haha.