BLLOD-PART-2-2.docx

**BLOOD GROUP MARKERS** - there are 33 blood group markers - ["blood group" ] refers to the entire blood group system comprising red blood cell (RBC) antigens whose specificity is controlled by a series of genes that can be allelic or linked very closely on the same chromosome.  - ["Blood...

**BLOOD GROUP MARKERS** - there are 33 blood group markers - ["blood group" ] refers to the entire blood group system comprising red blood cell (RBC) antigens whose specificity is controlled by a series of genes that can be allelic or linked very closely on the same chromosome.  - ["Blood type" ] refers to a specific pattern of reaction to testing antisera within a given system. **How are blood groups important in forensics?** - it can show the possible match of two samples. - it can show that two samples do not match and could have not had the same origin. This result is known as \"exclusion\" and is a very important concept in criminal investigations. -  forensic blood typing serves both as a confirmatory test and provides information about the suspect in the form of their blood type. - Even though blood typing cannot point to a specific person as the criminal, it can point to a group of people that share the same blood type. ABO BLOOD GROUP (most popular) - Discovered by Karl Landsteiner, an Austrian scientist in the year 1900 and later on won a Nobel prize for this discovery. - is classified into four types [based] on the a\. presence or absence of antigens on the red blood cells surface and b\. plasma antibodies. - **Group A **-- contains A antigen on RBC surface and B antibody on plasma - **Group B ** contains B antigen on RBC surface and A antibody on plasma - **Group AB** ** ** contains both A and B antigens on RBC surface and NO antibodies on plasma (neither A nor B). - **Group O ** contains neither A nor B antigen on RBC surface and but with both antibodies A and B on plasma **Rh Factors** - Scientists sometimes study **Rhesus** **monkeys** to learn more about the human anatomy because there are certain similarities between the two species. While studying Rhesus monkeys, a certain blood protein was discovered. This protein is also present in the blood of some people. Other people, however, do not have the protein. - The presence of the protein, or lack of it, is referred to as the Rh (for **Rhesus**) factor. - 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-). ] BLOOD TYPING We look for **agglutination or clumping**  **Bloodstain pattern analysis (BPA)** - is the interpretation of bloodstains at a crime scene in order to recreate the actions that caused the bloodshed. - Analysts examine the size, shape, distribution and location of the bloodstains to form opinions about what did or did not happen. - BPA helps reconstruct the crime and identify the perpetrator - uses principles of biology (behavior of blood), physics (cohesion, capillary action and velocity) and mathematics (geometry, distance, and angle) to assist investigators in answering questions such as: 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 - One of the most important functions of bloodstain pattern analysis is [to support or corroborate witness statements and laboratory and post-mortem findings.] - For example, if the medical examiner determines the cause of death is blunt force trauma to the victim's head, the pattern and volume of blood spatter should be consistent with a blunt instrument striking the victim one or more times on the head **HISTORY OF BPA** - **Eduard Piotrowski** considered the earliest known person to study on blood spatters (1895 - **Balthazard** ** **was first to analyze the  meaning of the spatter pattern (1939) - **Paul Kirk**. showed the position of the victim and assailant as well as showing that the assailant struck the victim with his left hand. - **Dr. Herbert MacDonell** published concerning the Flight Characteristics Of Blood and Stain Patterns in 1971. He founded the IABPA in 1983 where BPA continues to grow and develop **DEFINITION OF 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 break from the parent spatter when the 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. **Cast-off** -- blood that is thrown from an object in motion **Area of Convergence -** The area containing the intersections generated by lines drawn through the long axes of individual stains that indicates in two dimensions the location of the blood source. **Backspatter Pattern** - A bloodstain pattern resulting from blood drops that traveled in the opposite direction of the external force applied; associated with an entrance wound created by a projectile. **Blood Clot** - A gelatinous mass formed by a complex mechanism involving red blood cells, fibrinogen, platelets, and other clotting factors. **Bloodstain** - A deposit of blood on a surface. **Drip Pattern** - A bloodstain pattern resulting from a liquid that dripped into another liquid, at least one of which was blood.. **Flow Pattern** - A bloodstain pattern resulting from the movement of a volume of blood on a surface due to gravity or movement of the target. **Forward Spatter Pattern** - A bloodstain pattern resulting from blood drops that traveled in the same direction as the impact force. **Impact Pattern** - A bloodstain pattern resulting from an object striking liquid blood.. **Mist Pattern** - A bloodstain pattern resulting from blood reduced to a spray of micro-drops as a result of the force applied. **Plasma** - The clear, yellowish fluid portion of blood. **Platele**t - An irregularly shaped cell-like particle in the blood that is an important part of blood clotting. Platelets are activated when an injury causes a blood vessel to break. They change shape from round to spiny, "sticking" to the broken vessel wall and to each other to begin the clotting process **Projected Pattern** - A bloodstain pattern resulting from the ejection of a volume of blood under pressure, such as a spurt or spray. DROP OF BLOOD **TYPES of STAINS** **A. Passive Bloodstains** Stains created by force of gravity acting on an injured body Examples : drops, flows and pool, clots **B.Transfer Bloodstains** result from objects coming into contact with existing bloodstains and leaving wipes, swipes or pattern transfers behind such as a bloody shoe print or a smear from a body being dragged  may be used to identify an **object** or **body** part. 1\. wipe = created from an object [moving through] a bloodstain 2\. Swipe =created from an object [leaving] a bloodstain. **C.Spatter Bloodstains** Patterns that occur when a **force** is applied to the **source** of the blood Can be projected/impact **Projected** 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.) Bloodstain patterns resulting from blood exiting the body under pressure from a breached artery Example: when a big artery or vein in the neck area will be cut/slashed. 2**. Cast-off stains** Blood released or thrown from a blood-bearing object in motion is usually caused by blood from an internal injury mixing with air from the lungs being expelled through the nose, mouth or an injury to the airways or lungs. **IMPACT Spatter** Spatters can also be classified as 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 **Droplet flight dynamics/characteristics** **Phases of Drop Impact** +-----------------------+-----------------------+-----------------------+ | **PHASE** | **description** | | +=======================+=======================+=======================+ | **1.**Contact & | Collapses from the |  | | Collapse | bottom up | | | | | | | | Blood pushed outward | | | | into a rim | | +-----------------------+-----------------------+-----------------------+ | **2.** Displacement | slight dimples and | | | | spines begin to form | | | | based on the | | | | irregularities on the | | | | surface of impact | | +-----------------------+-----------------------+-----------------------+ | **3.** Dispersion | Creates satellite |  | | | spatter | | +-----------------------+-----------------------+-----------------------+ | **4.** retraction | | | +-----------------------+-----------------------+-----------------------+ **Factors that affect spatter appearance** 1.Size of the droplet 2\. Angle of impact  The more acute the angle of impact, the more elongated the stain. = 90-degree angles are perfectly round drops; = 80-degree angles take on a more elliptical shape. = At about 30 degrees the stain will begin to produce a tail. 3\. Velocity at which the blood droplet left its origin The greater the velocity, the lesser is the diameter of the stains 4\. Height The diameter of the stain will increase as height increases; 5\. Texture of the target surface The type of surface the blood strikes affects the nature of the observed splatter pattern. - [Hard smooth surface] (e. g. , glass): little distortion around the edges of the droplet. -- \- [Irregular linoleum flooring]: often show distortion (scalloping) around the edge of the droplets. \- [Wood or concrete]: distorted to a larger extent (e. g. , spines and secondary splatter).