Bloodstain Pattern Analysis… Bloodspatter http://www.youtube.com/watch?v=6Cn8Fcwcq8s&feature=related 1

Blood – Distinct Properties Blood forms a spherical shape (perfect circular shape) Surface Tension causes the blood drop to pull itself in; both horizontally and vertically.

Overview…at the end of this unit you will be able to Determine Height and Angle of Blood Source Determine Direction of Blood – Directionality Determine types of Blood Stain Patterns – low, medium and high velocity Determine type of weapon used

What does a blood spatter analyst do? http://www.youtube.com/watch?v=Od8YuwUT794&safety_mode=true&persist_safety_mode=1 Directionality http://www.youtube.com/watch?v=zmPFZA_BpaE

Blood Spatter Blood drops form different shapes and sizes Blood spatter analysis uses the shapes and sizes to reconstruct the crime scene.

Blood Spatter Factors affecting the size of the drop… Consider the surface Consider if it was a single drop or multiple drops Consider the height the drop fell

Blood Drop Animation. Formation of drop. Distinct blood drop pattern Blood Drop Animation * Formation of drop * Distinct blood drop pattern * Angle of impact http://projects.nfstc.org/gallery/main.php?g 2_itemId=3857

Blood drops fall as small spheres Determining Distance Blood Falls Blood drops fall as small spheres

Determining Distance Blood Falls Drops form a circle when hitting surface Size depends on height & speed of blood drop and surface it hits

Determining Distance Blood Falls Blood Spatter > Distance Determining Distance Blood Falls Faster drop = larger diameter (size) Higher distance = larger diameter Due to air resistance, speed maxes out at distances above about 7 feet

Determining Distance Blood Falls Blood Spatter > Distance Determining Distance Blood Falls However, size of drop also depends on the volume of the drop. Volume depends on the object blood originated from (needle = small; bat = large).

Determining Distance Blood Falls Blood Spatter > Distance Determining Distance Blood Falls After approximately 7 ft or 2 m, the diameter of the blood drop remains the same

Effect of Surface on shape of blood drop Blood Spatter Effect of Surface on shape of blood drop Smooth surface = smooth sphere Rough surface may cause some spatter or spines

1 drop of blood dropped from 12 inches, glass, cardboard and concrete….

1 drop of blood dropped from 12 inches, newspaper, paper towel, and carpet ….

Lab Activity… Comparing diameter of blood drops from different heights Comparing edges and diameter of blood drops on different surfaces Comparing blood drops at different angles

Determining Direction of Blood Blood Spatter > Direction Determining Direction of Blood Narrow end of a blood drop will point in the direction of travel.

Determining Direction of Blood Blood Spatter > Direction Determining Direction of Blood If more than one drop (from spatter) results, the point or area of origin can be determined

Determining Direction of Blood Blood Spatter > Direction Determining Direction of Blood If more than one drop (from spatter) results, the point or area of origin can be determined

Determining Direction of Blood Blood Spatter > Direction Determining Direction of Blood This is a 2-dimensional point of origin. It is possible to determine the 3-D point of origin

Determining Angle of Blood (Impact) AOI Blood Spatter > Direction Determining Angle of Blood (Impact) AOI 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 the angle of impact

AOI = Width of blood drop / length

Blood Spatter > Direction Once Directionality and AOI are determined, a string can be guided back to the point of origin. This will show the site of blood origin and angle the victim was positioned.

Using the AOI and directionality of blood drop; one can determine the height of the source (victim?)

Blood Spatter Types of Spatter Spattered Blood = random distribution of bloodstains that vary in size Amount of blood and amount of force affect the size of blood spatter. Can result from gunshot, stabbing, beating

Blood Spatter Spattered Blood can: Help determine the location of the origin of the blood source. Help determine the mechanism which created the pattern.

Blood Spatter Spattered Blood In general, the higher the velocity the more spread out the droplets are and the individual stains are smaller. Low impact/low velocity 7mm+ – 3.1 mm Medium impact/medium velocity 3.0 – 1.1 mm High impact/high velocity = gunshot <1mm

Low velocity… Droplets are 3.1mm in diameter or larger beating or hitting (after the first blow)

Medium velocity…. Droplets are 1.1-3 mm in diameter Caused more by force and less by gravity blunt force trauma, i.e. baseball bat, ‘billy club’, stabbings

High velocity… less than 1mm in diameter takes on a "mist like" appearance gunshot

Blood Spatter Types of Spatter Gunshot Spatter = can result in a mist-like spatter that indicates a gunshot. Not all gunshots will result in misting. If misting is present, it is most likely a gunshot.

Gunshot Spatter Gunshots result in back spatter (where bullet enters) Blood Spatter Gunshot Spatter Gunshots result in back spatter (where bullet enters) and forward spatter (where bullet exits).

Blood Spatter Types of Spatter Beating and Stabbing Spatter = larger individual stains, usually castoff pattern also present. First blow usually doesn’t result in spatter since there is not yet any exposed blood.

Blood Spatter Types of Spatter Satellite Spatter = free falling drops of blood that fall onto a spatter pattern. These drips are usually much larger than impact spatter. However, blood dripping into blood can create a spatter.

Types of Spatter Castoff Pattern = Blood flung off of swinging object. Blood Spatter Types of Spatter Castoff Pattern = Blood flung off of swinging object. Can reconstruct where assailant and victim were positioned.

Blood Spatter Types of Spatter Expirated Bloodstain Pattern = Blood can accumulate in lungs, sinuses, and airway. Forcibly exhaled. Can appear like beating or gunshot pattern. May be mixed with saliva or nasal secretions.

Transfer - Wipe or a swipe.. Transfers occur when a blood source comes in direct contact with a target surface area. Blood is moved or ‘transferred’ to a new surface

Alteration of bloodstain over time Blood Spatter Alteration of bloodstain over time Blood dries and clots over time. Difficult to estimate the time the blood exited the body. Clotted smears can indicate time of movement.

Blood spatter tutorials: http://www.sho.com/site/dexter/blood_s patter.do Dexter - Arterial Spurts Dexter - Cast Off Stains Expiratory Blood Blood Swipe/Wipe Blood Shadowing and Ghosting Point of Impact Blood Transfer