BLOOD SPATTER ANALYSIS Jennifer Pechal

Blood stain pattern analysis “When liquid blood is acted upon by physical forces, bloodstains and bloodstain patterns may be deposited on various…patterns can yield valuable information concerning the events which lead to their creation when examined by a qualified analyst.  ” (IABPA) “The examination of the shapes, location, and distribution patterns of blood stains, in order to provide an interpretation of the physical events which gave rise to their origin.” (J. Slemko Forensic Consulting)

Why is it important in forensics? Confirm or refute assumptions concerning events and their sequences Suspect’ s account Victim’s account Bloodstain evidence may reveal: Area(s) of origin Number of blows or shots Type and direction of impact that produced bloodshed Movement and direction of a person or object Movement of victim after bloodshed Potentially the assailant Reconstruct events

History 1895 – Dr. Eduard Piotrowski published first reference to bloodstain pattern analysis 1939 – Dr. Victor Balthazard the first to use physical interpretation of stains 1955 – Dr. Paul Kirk used blood stain evidence in State of Ohio v Samuel Sheppard 1973 – Dr. Herbert MacDonell conducted first training program for blood spatter in Jackson, MS

Blood Makes up approximately 8% of the weight in a human body Males have approximately 5 – 6 L Females have approximately 4 – 5 L Blood comprised of two parts: Hematocrit Red blood cells White blood cells Platelets Plasma Gases Ions Nutrients molecules Proteins, fats, hormones

Properties of blood Some blood properties can be compared to water: Blood is 6x more viscous than water Gravity of blood is slightly higher Blood droplets stay round because of surface tension Water Blood Viscosity 1.0 mP·s-1 3-4 mP·s-1 Surface tension 0.073 N·m-1 0.058N·m-1 Density 1000 kg/m3 1060 kg/m3

Surface Tension Surface tension is an upwards force that allows the surface of a liquid to act as an elastic sheet Free falling blood will stay intact until acted upon by an exterior force When it strikes another object When acted upon by another force

Phases of impact 1. Contact/Collapse Droplet hits the object Collapses from the bottom up

Phases of impact 2. Displacement Slight dimples and spines begin to form based on the irregularities on the impact surface Top view Side view

Phases of impact 3. Dispersion Most of the volume of the blood is forced to the rim Create satellite spatter Top view Side view

Phases of impact 4. Retraction Surface tension trying to keep the droplet together Satellite spatters that have enough momentum can form completely separate stains The droplet can “burst” if the force pulling it apart is great enough Side view Top view

Size and Shape A blood droplet released from a shorter height will be smaller than a blood droplet released from a higher height Spatter size is dependent upon velocity Low velocity spatter = 5 ft/sec Medium velocity spatter = 5 – 25 ft/sec High velocity spatter = 100+ ft/sec

Low velocity spatter 3 mm or greater in diameter Blood falls under the influence of gravity Blood trail motion can prove directionality Result from weapon cast-off, a person remaining still, walking, or running

Medium velocity spatter 1 – 3 mm in diameter Indicates blunt force trauma, sharp trauma, or cast- off

High velocity spatter Smaller than 1 mm in diameter Appears as a fine spray or misting Resulting from gunshot trauma, power tools, an object striking with extreme velocity, or an explosion

Directionality width = 1.0, length =1.0, which corresponds to an impact angle of 90 degree width = 1.0, length = 2.0, which corresponds to an impact angle of 30 degrees sin i = (width/length) arcsin i = angle of impact

What direction did the blood originate?

Area of convergence Determine directionality of the blood droplets Lines must be drawn away from the direction of travel towards the origin Draw straight lines using the “oval” of the blood droplet Lines should run along the length The direction of the blood droplet Measure from the back of the stain Area of convergence

Area of origin Identify the AOC this will be the z- axis Calculate the angle of impact for each blood droplet Attach a string for each droplet at it’s specific angle to the z-axis Repeat for each droplet

Types of blood spatter Arterial

Types of blood spatter Transfer

What caused this pattern?

A gun impression

What caused this pattern? Hair

What caused this pattern? Flies

What caused this pattern? Maggots

Questions?