Blood Spatter Analysis

Blood and Life Blood Volume On average, blood accounts for 8 % of total body weight 40% of total blood volume loss, externally or internally is usually considered to be fatal ...

What is Blood Spatter Analysis? A field of forensic examination of the shapes, locations, and distribution patterns of bloodstains, in order to provide an interpretation of the physical events which gave rise to their origin.

What does it tell us? 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

While a reconstruction could tell some more about…. 1. Stain condition 2. Pattern 3. Distribution 4. Location 5. Directionality

How is blood evidence detected at a crime scene? Light Source Investigators will first examine the crime scene to look for areas that may contain blood. They may 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. Blood Reagent Tests These tests, referred to as presumptive tests, are used to 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. Examples: Phenolphthalein is a chemical that is still utilized today and is usually referred to as the Kastle-Meyer test and produces a pink color when it reacts with hemoglobin. HemaStix is a strip that has been coated with tetramethylbenzidine (TMB) and will produce a green or blue-green color with the presence of hemoglobin. HemaStix

Fluorescein Reaction in UV Light Luminol This chemical is used by crime scene investigators to locate traces of blood, even if it has been cleaned or removed. Investigators spray a luminol solution is throughout the area under investigation and look for reactions with the iron present in blood, which causes a blue luminescence. One problem is that other substances also react, such as some metals, paints, cleaning products, and plant materials. Another problem is that the chemical reaction can destroy other evidence in the crime scene. Luminol Reaction Fluorescein This chemical is also capable of detecting latent or old blood, similar to luminol. It is ideal for fine stains or smears found throughout a crime scene. After the solution has been sprayed onto the substance or area suspected to contain blood, a UV light and goggles are used to detect any illuminated areas, which appear greenish-white if blood is present. It may also react to many of the same things as luminol (copper and bleach). Fluorescein Reaction in UV Light LCV or Leuco Crystal Violet, is one type of chemical process that is used for blood enhancement. Using this test helps to make the blood evidence more visible so it can be photographed and analyzed.

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

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

More terminology… Angle of impact: angle at which blood strikes a target surface Bloodstain transfer: when a bloody object comes into contact with a surface and leaves a patterned blood image on the surface Back-spatter: blood that is directed back toward the source of energy Cast-off: blood that is thrown from an object in motion Directionality—relates to the direction a drop of blood travels in space from its point of origin Contact stain: bloodstains caused by contact between a wet blood-bearing surface and a second surface that may or may not have blood on it Transfer—an image is recognizable and may be identifiable with a particular object Swipe—wet blood is transferred to a surface that did not have blood on it Wipe—a non-blood-bearing object moves through a wet bloodstain, altering the appearance of the original stain

Passive Bloodstains Patterns created from the force of gravity Passive Bloodstains Patterns created from the force of gravity. Drop, series of drops, flow patterns, blood pools, etc.

Projected bloodstains Projected bloodstains are created when an exposed blood source is subjected to an action or force, greater than the force of gravity. (Internally or Externally produced) The size, shape, and number of resulting stains will depend, primarily, on the amount of force utilized to strike the blood source.

What inferences can you make based on this picture?

Blood released or thrown from a blood-bearing object in motion Cast-off Stains Blood released or thrown from a blood-bearing object in motion

Back-spatter: blood that is directed back toward the source of energy

Arterial Spurt / Gush Bloodstain pattern(s) resulting from blood exiting the body under pressure from a breached artery:

Arteries… The arteries are the blood vessels that deliver oxygen-rich blood from the heart to the tissues of the body. Each artery is a muscular tube lined by smooth tissue and has three layers: The largest artery is the aorta, the main high-pressure pipeline connected to the heart's left ventricle. The aorta branches into a network of smaller arteries that extend throughout the body. The arteries' smaller branches are called arterioles and capillaries.

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.

Droplets could be altered… think about your experiments during the Jigsaw project… Size of the droplet Angle of impact Velocity at which the blood droplet left its origin Height Texture of the target surface On clean glass or plastic—droplet will have smooth outside edges On a rough surface—will produce scalloping on the edges

IMPACT SPATTER Blood stain patterns created when a blood source receives a blow or force resulting in the random dispersion of smaller drops of blood. It depends on spreading behavior / surface texture and velocity

Stages of impact

Stages of Drop Impact 1. Contact & Collapse 2. Displacement Image used with permission from Tom Bevel & Ross Gardner, June 2006.

Stages of Drop Impact 3. Dispersion 4. Retraction

Angle of Impact The shape of a blood drop: Chapter 10 90° angles are perfectly round drops 80° angles take on a more elliptical shape. At about 30 ° the stain will begin to produce a tail. The more acute the angle of impact, the more elongated the stain. The more acute the angle, the easier it is to determine the direction of travel. The shape of a blood drop: Round—if it falls straight down at a 90° angle Elliptical—blood droplets elongate as the angle decreases from 90° to 1°. The angle can be determined by the following formula: Kendall/HUnt

Angle of Impact

Size and Velocity Low velocity spatter usually produced by gravity alone, or minimal force, or by an object dropping into and splashing blood from a blood pool. It results from an applied force of up to 5 feet per second and produces drops that are 4mm or larger. Medium velocity spatter predominantly small drops with diameters between 1mm and 3mm. Normally associated with blunt force trauma with an applied force between 5 to 25 feet per second. High velocity spatter is very fine droplets, usually less than 1mm in diameter. These stains are produced from an applied force of 100 feet per second or faster. Gunshot exit wounds or explosions commonly produce this type of spatter.

Medium impact occurs when a force such as a bat is applied. Low impact is really blood under the influence of gravity - it just falls.

High impact - fine mist of droplets Image courtesy Stuart James, February 2007

TARGET SURFACE TEXTURE Blood droplets that strike a hard smooth surface, like a piece of glass, will have little or no distortion around the edge.

TARGET SURFACE TEXTURE Blood droplets that strike linoleum flooring take on a slightly different appearance. Notice the distortion (scalloping) around the edge of the blood droplets.

TARGET SURFACE TEXTURE Surfaces such as wood or concrete are distorted to a larger extent. Notice the spines and secondary spatter present.