Image via Wikipedia
Blood is a big part of my life. I don’t mean the blood flowing through my veins - though yes, that’s a really big part of my life. I mean the all over the place kind of blood. I have children. My house often looks like a crime scene, as I explained in my Wirters' Police Academy Intro.
WPA 2011 Blog article
But also, my youngest daughter is a type 1 diabetic. I prick her finger, and use her blood, an average of 21 times a day to figure things out. A drop of blood is analyzed by her meter giving me a snap shot of what’s going on in her body. Is it the whole picture? No. Is it the big picture? No. It’s just a momentary snippet of information. In that moment, I had an idea of what was happening. Putting all of these snippets of information together day after day, week after week, helps me to form my ideas as to what the bigger picture of my daughter’s health looks like.
This is my understanding of how a forensic scientist goes to work. Each piece of information is added to other information, and soon a picture starts (hopefully) to form. Today, we revisit our hero Dave Pauly whom we met when he was teaching us about how to see "Crime in a Different Light." In this chapter, our forensic specialist is involved in getting a picture of what could have happened to create the blood covered crime scene.The big name for all of this is “Blood Stain Pattern Analysis” or BSPA. The goal here is to determine velocity, direction and point of origin.
IMPORTANT - PLEASE BE AWARE THAT THIS BLOG CONTAINS LINKS TO GRAPHIC IMAGES. PLEASE CONSIDER YOUR TOLERANCE LEVEL BEFORE YOU REDIRECT TO ANY OF THE VIDEO.
Mechanisms o:f Deposition:
Passive - clot, drip, pool, flow saturation, serum separation.
Transfer - swipe and wipe
Projected - arterial spurts, cast off, expiration, splashes
Miscellaneous - fly spots, voids
Transfer Patterns - occur when an object that has blood on it rests on a surface leaving an
Swipe and Wipe Patterns - occur when there is blood on a surface and something moves
through the blood.
Cast Off Pattern - occurs when there is blood on an object and the blood is flung off as
the object is swung through the air.
Shadowing and Ghosting - these are void patterns where an object or person was in
place as blood patterning took place and then the person or object
Blood dropping onto blood - self explanatory, creates small droplets
Point of impact - how an object impacts a blood source
Arterial Spurts - When an artery has been breached it releases blood with great velocity
Expiratory - occurs when blood is coughed or sneezed. It is a fine misting. This also
occurs when there is a gun shot and the bullet leaves with velocity.
The tail of the blood droplet points to the direction from which it came.
Blood will change its pattern based on the angle at which it contacted the surface. Once you know the angle the forensic scientist can use a protractor to attach strings and find the spot in which the victim had been. This is a geometric calculation and they are looking for an area of convergence.
Video Quick Study (3:11) Dexter Blood Spatter
Video Quick Study (2:01) Examining blood stains
Video Quick Study (8:14) Studying blood stains
Video Quick Study (2:17) Blood spatter 101 - very interesting use
Video Quick Study (12:07) part 1 of an academic lecture
link prt2 (7:40)
THE USE OF LCV - is a chemical substance that is used to check for blood in -
* Missing person cases where a crime is suspected.
* Areas where a suspected violent crime occurred but it has been cleaned/bleached
* Visible substances suspected to be blood
Luminol experiment:Video Quick Study (2:49) Luminol
Video Quick Study (13:24) BlueStar - is visible longer and is now the go to for many CSI investigators.
LCV is readily mixed in the field. It has 0% false positives, BUT this does not mean that you can determine if it is animal blood or human blood. Hmmm that’s where your plot could thicken.
Did you know they can use LCV to find blood on a wall that has 9 coats of paint on it? The blood can be over 30 years old and the LCV still works?
There should be no ambient light. They spray a fine mist over the target area and if ther eis blood it will show up for a few seconds as bright green. There is a product called Lumiscene that lasts much longer allowing for better photography.
So how do you know if this evidence will be admissible in court? The products used must meet general acceptance standards.
While not a fan of Wikipedia, I am supplying these links as a starting point for your research:
Daubert V. Merrell Dow Pharmeceuticals LINK
Frye v. USA LINK
I hope this helps. Feel free to leave a question or a comment below.
And why not take a moment to +1 this page and send a link to your friends on Facebook and Twitter? Buttons conveniently placed below.