Forensic Science Lab Activity Bloodstain Science Forensic Science Lab Activity Warning: Some material in this presentation and related videos may be too graphic for some people. T. Trimpe 2006 http://sciencespot.net/

What does the abbreviation BPA represent? Bloodstain Pattern Analysis What can an investigator learn from the analysis of a blood spatter?  Type and velocity of weapon  Number of blows  Handedness of assailant (right or left-handed)  Position and movements of the victim and assailant during and after the attack  Which wounds were inflicted first  Type of injuries  How long ago the crime was committed  Whether death was immediate or delayed Source: http://science.howstuffworks.com/bloodstain-pattern-analysis1.htm How does a blood droplet form? Click the image for an animation then click phases of impact http://www.crimescenetwo.com/img/popup/book2p2.jpg

Detecting Blood Evidence Light Source Investigators will first examine the crime scene to look for areas that may contain blood. Use a high-intensity light or UV lights to help them find traces of blood as well as other bodily fluids that are not visible under normal lighting conditions

Detecting Blood Evidence Blood Reagent Tests presumptive tests detect blood at crime scenes based upon the properties of hemoglobin in the blood. Further tests at the crime lab can determine if it is human blood or not.

Blood Reagent Tests Kastle-Meyer test HemaStix Uses chemical phenolphthalein Produces a pink color when it reacts with hemoglobin Uses a strip coated with tetramethylbenzidine (TMB) Produces a green or blue-green color in the presence of hemoglobin

Detecting Blood Evidence Luminol Chemical is used to locate traces of blood, even if it has been cleaned or removed. Reacts with the iron present in blood and causes a blue luminescence. Disadvantages: Can reacts with other substances (paints, cleaning products, plant materials, some metals) Chemical reaction can destroy other evidence in the crime scene.

Luminol

Detecting Blood Evidence Fluorescein Chemical capable of detecting latent or old blood, similar to luminol. UV light and goggles are used to detect any illuminated areas after stain is sprayed Stains appear greenish-white if blood is present.

Detecting Blood Evidence Leuco Crystal Violet or LCV chemical process that is used for blood enhancement helps to make the blood evidence more visible so it can be photographed and analyzed.

Click picture for video Video Clip Click picture for video

Blood Stain Pattern Analysis

Blood Stain Pattern Analysis The bloodstain patterns left by falling, projected or smeared blood can be analyzed by trained crime scene investigators. Careful observation and measurement of the position and shape of bloodstains can give lots of information about the direction of travel, angle of impact and the speed or velocity of the blood droplets.

Types of Bloodstain Patterns Passive Bloodstains Patterns created from the force of gravity Drop, series of drops, flow patterns, blood pools, etc. Projected Bloodstains Patterns that occur when a force is applied to the source of the blood Includes low, medium, or high impact spatters, cast-off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound. Transfer or Contact Bloodstains These patterns are created when a wet, bloody object comes in contact with a target surface; may be used to identify an object or body part. A wipe pattern is created from an object moving through a bloodstain, while a swipe pattern is created from an object leaving a bloodstain. Images from http://www.bloodspatter.com/BPATutorial.htm

Bloodstain Pattern Analysis Terms Spatter – Bloodstains created from the application of force to the area where the blood originated. Origin/Source – The place from where the blood spatter came from or originated. Angle of Impact – The angle at which a blood droplet strikes a surface. Parent Drop – The droplet from which a satellite spatter originates. Satellite Spatters – Small drops of blood that break of from the parent spatter when the blood droplet hits a surface. Spines – The pointed edges of a stain that radiate out from the spatter; can help determine the direction from which the blood traveled. Parent Drop Spines Satellite Spatters

Traveling Blood Droplets When a force is applied to a mass of blood, the blood breaks into droplets The droplets fly through the air as “perfect” spheres due to surface tension Surface tension enables blood droplets to maintain a sphere shape.

Stages of impact

Stage 1: contact & collapse Image used with permission from Tom Bevel & Ross Gardner, June 2006.

Stage 2: displacement Image used with permission from Tom Bevel & Ross Gardner, June 2006.

Stage 3: dispersion Image used with permission from Tom Bevel & Ross Gardner, June 2006.

Stage 4: retraction Image used with permission from Tom Bevel & Ross Gardner, June 2006.

Click picture to review stages of impact Stages of Impact Video Click picture to review stages of impact

Height and size of blood drops A blood droplet released from a 1m height will be smaller than a blood droplet released from a 1.5m height. Higher height = higher velocity = larger droplet This is because the velocity of the blood droplet released from a higher height is greater.

Surface and shape of blood drops Images courtesy DUIT Multimedia: Paul Ricketts.

Low impact Velocity: 5 f/s, 1.5 m/s Low impact is really blood under the influence of gravity - it just falls. Velocity: 5 f/s, 1.5 m/s • Free-falling drops (gravity only) • Cast off from fist, weapon, etc. • Dripping (blood droplets into themselves) • Splashing (stepping, throwing, etc.) • Arterial spurting Image courtesy UWA PhD research student Mark Reynolds.

Arterial spurting

Medium impact Medium impact occurs when a force such as a bat is applied. Velocity: 25 - 100 f/s, 7.5 - 30 m/s) Image courtesy UWA PhD research student Mark Reynolds.

High impact - fine mist of droplets Velocity: >100 f/s, >30 m/s Gun shot or machinery Image courtesy Stuart James, February 2007

Angle of impact Image used with permission from Stuart James, February 2007.

Angle of Impact Animation Click picture for animation, then click on angle of impact tab

Determining Direction of Blood The angle can be determined mathematically. Width/Length, then take the inverse sin (sin-1). This number is the impact angle (90 = perpendicular to surface; <10 at a sharp angle)

Determining Point of Origin ©2010 Elsevier, Inc.

Dexter explains Blood Spatter Click picture for video

Reconstructing the crime With the evidence that is collected, the crime scene investigator attempts to reconstruct the crime. This involves trying to work out what events happened and the order that they happened. Image courtesy UWA PhD research student Mark Reynolds.