Forensic BLOODStains Blood Pattern Analysis OUTLINE BLOOD properties

Forensic BLOODStains Blood Pattern Analysis

OUTLINE • BLOOD properties • BLOOD on CRIME SCENE • BLOOD STAINS: patterns • BLOOD SPATTERS

Blood Facts The average adult has about FIVE liters of blood in their body, which makes up 7 -8% of body weight. Whole blood is a mixture of ~55% plasma (liquid) and ~45% blood cells (solid). Blood is living tissue that carries oxygen and nutrients to all parts of the body, and carries carbon dioxide and other waste products back to the lungs, kidneys and liver for disposal. It also fights against infection and helps heal wounds, so we can stay healthy.

What makes up our blood? • RED BLOOD CELLS (Erythrocytes) – The most abundant cells in our blood; produced in the bone marrow and contain a hemoglobin that carries oxygen to our cells. • WHITE BLOOD CELLS (Leukocytes) – Being part of the immune system, they destroy infectious agents called pathogens. • PLASMA – The yellowish liquid portion of blood that contains electrolytes, nutrients and vitamins, hormones, clotting factors, and proteins such as antibodies to fight infection. • PLATELETS (Thrombocytes) – The clotting factors that are carried in the plasma; they clot together in a process called coagulation to seal a wound and prevent a loss of blood. • to clot – свертываться, сгущаться.

Genetics of Blood Types • Your blood type is established before you are BORN, by specific GENES inherited from your parents. • You inherit one gene from your MOTHER and one from your FATHER. • These genes determine your blood type by causing proteins called AGGLUTINOGENS to exist on the surface of all of your red blood cells.

What are blood types? There are 3 genes for blood type: A, B, & O. Since we have 2 genes, there are 6 possible combinations. http: //learn. genetics. utah. edu/units/basics/blood/types. cfm 4 Blood Types AA or AO = Type A BB or BO = Type B OO = Type O AB = Type AB

4 Major blood types 4 major blood types: O, A, B, and AB. How common are they? Most abundant O type, least abundant AB.

Rh Factors • Rhesus factor (Rh) defines the presence of a certain protein on the surface of red blood cells of some people. • If your blood does contain the protein, your blood is said to be Rh positive (Rh+). If your blood does not contain the protein, your blood is said to be Rh negative (Rh-). O+ OA+ AB+ BAB+ AB-

Blood Transfusions A blood transfusion is a procedure in which blood is given to a patient through an intravenous (IV) line in one of the blood vessels. Blood transfusions are done to replace blood lost during surgery or a serious injury. I Who can give you blood? People with TYPE O blood are called Universal Donors, because they can give blood to any blood type. People with TYPE AB blood are called Universal Recipients, because they can receive any blood type. Rh + Can receive + or Rh - Can only receive - Universal Donor II IV Universal Recipient

Blood in Crime Scene Investigations Blood as Class Evidence - Blood typing can be used as class evidence because more than one person has the same blood type. - This can narrow the suspect list by excluding people with different blood types Blood as Individual Evidence - White blood cells contain DNA, so it is possible to determine the origin of the blood by doing DNA profiling - This can link a blood sample to a specific individual

Blood in Crime Scene Investigations IF you put A blood into B person, blood will agglutinate (gets clumpy) • What do forensic scientists do with blood? • They conduct tests to answer the following questions: • – Is it blood? – Is it human blood? – What type of human blood?

IS IT BLOOD? • Presence of blood if not obvious, can be tested at the crime scene: Kastle-Meyer test or Phenolphthalein. • Swab with phenolphthalein, possible blood and hydrogen peroxide pink stain: positive for blood. • Luminol, Blue. Star causes blood to fluoresce: requires darkened room. • These are presumptive blood tests – Fast, easy, inexpensive – May be false positives (in the presence of some vegetable materials) • Confirmatory tests then needed (more reliable) 12

IS IT HUMAN BLOOD? • Confirmatory tests ANSWER THE QUESTION: • Is it human blood? – Inject human blood into animal; it produces antihuman antibodies – Process the animal’s blood to recover antibodies – Sensitive test and may be done with dried blood stains over 15 years old. – Gel diffusion test available or electrophoretic test (test run with electric field on gel which causes the antigen antibody line to form. 13

Blood Evidence • Blood samples – Can be analyzed to determine blood type and DNA, which can be matched to possible suspects. • Blood droplets – Can be analyzed to give clues to the location of a crime, movement of a victim, and type of weapon. • Blood spatter – Can be analyzed to determine patterns that give investigators clues to how a crime might have happened.

Blood Stain Patterns • The location, distribution, and appearance of bloodstains and spatters is useful for interpreting and reconstructing the events that produced the bleeding. 15

Document the Crime Scene • Documenting the crime scene allows for later reconstruction to let the evidence tell the crime story. • You document the scene with: – Photos/ video – Drawings – Notes of observations

Blood Stains Tell a Story • What information could be obtained from the bloodstain pattern at a crime scene? – Direction of travel (directionality), – The angle of impact, – The position of origin, – Blood droplet’s speed at time of impact.

Categories of Bloodstains Passive Bloodstain Transfer Bloodstain Spatter Example: Projectile Bloodstain

Categories of Bloodstains 1) Passive Bloodstains - Drops are created or formed by the force of gravity acting alone - Examples: - Drops - Drip patterns - Pools - Clots

Categories of Bloodstains 2) Transfer Bloodstains When an object with blood on it touches one that does not have blood on it, this produces a transfer (or contact) pattern. • Examples of transfers with features include fingerprints, handprints, footwear prints, tool prints, and fabric prints in blood. - Examples of transfer bloodstains are: contact bleeding, smear, wipe

Categories of Bloodstains 3) Blood spatter - 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 on the amount of force used to strike the blood source

Categories of Bloodstains Projected Bloodstains - Examples - Arterial Spray /Gush – is caused by opening a major artery or the heart: it sprays out a large volume of blood with each heart beat.

Categories of Bloodstains Projected Bloodstains Cast-off stains – Blood released or thrown from a blood bearing object in motion

Categories of Bloodstains Projected Bloodstains Impact Spatter – bloodstain patterns created when a blood source receives a blow or force resulting in the random dispersion of smaller drops of blood. Low velocity Spatter Medium velocity Spatter High Velocity Spatter

Low Velocity Spatter • The characteristics of a low velocity spatter are the pattern consists of large separate or compounded drops with diameters ≥ 3 mm, produced by minimal force and hits the surface with < 1. 2 m/s velocity • Dripping Blood from a wound:

Medium Velocity Blood Spatters • Medium velocity spatter consists of small drops with diameters of 1 -3 mm. • They travel at an average of 1. 2 to 6 m/s • They are commonly associated with blunt force trauma.

High Velocity Blood Spatters • High velocity spatter: it consists of small drops with diameters < 1 mm. This blood spatter hits at > 30 m /s. Gunshot spray.

Direction of Bloodstains - A drop of blood hitting a surface perpendicular (90 degrees) will result in a circular stain - Blood that strikes a surface at an angle less than 90 degrees are elongated or have a teardrop shape - Directionality: the pointed end of the stain (tail) will always point in the direction of travel

Impact Angle Determination - Angle of Impact is the acute angle formed between the direction of the blood drop and the plane of the surface it strikes A drop of blood at a 90° angle gives a nearly circular stain. As the angle decreases, the stain elongates By accurately measuring the length and width of a bloodstain, the impact angle can be calculated using the SIN formula below

Stain Patterns of Blood • Surface texture is important: The harder and less porous the surface, the less spatter results. • The direction of travel of blood striking an object may be found: the pointed end of a bloodstain always faces its direction of travel. 30

Blood Fall Height • Initial height of the blood drop affects the pattern of blood drops: the higher the drop, the bigger the velocity and the larger the diameter

Stain Patterns of Blood • The origin of a blood spatter in a twodimensional configuration can be established by drawing straight lines through the long axis of several individual bloodstains. The intersection or point of convergence of the lines represents the origin point.

Wound Characteristics • The location of injury, the size of the wound created, and the distance between the victim and the muzzle of the weapon all affect the amount of back spatter that occurs.

Expirated Patterns of Blood • A pattern created by blood that is expelled from the mouth or nose from an internal injury is called an expirated blood pattern: lighter in color (mix with saliva), possible bubbles (breath). 34

Void Pattern • A void is created when an object blocks the deposition of blood spatter onto a target surface or object.

Blood Pooling • A pool of blood occurs when blood collects in a level (not sloped) and undisturbed place. • The edges of a stain will dry to the surface, producing a phenomenon called skeletonization. • Drying time is dependent on environmental factors

Documenting Bloodstain Evidence • Investigators should note, study, and photograph each pattern and drop of blood to record the location of specific patterns and to distinguish the stains from which laboratory samples were taken. 37

Documentation The investigator should create photographs and sketches of the overall pattern to show the orientation of the pattern to the scene.

Grid Method • Two common methods of documenting bloodstain patterns are • the grid method and • the perimeter ruler method.

Perimeter ruler method

Which of the three blood droplets shown would have been created by a wound in the lower part of the leg? Explain. If you have a blood droplet as shown here, what does it tell you? Explain. If you find a trail of blood with droplets that are round and close together, what could this mean?