Blood and Blood Spatter Serology Blood Spatter Analysis
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Blood and Blood SpatterSerologyBlood Spatter Analysis
What is serology?Serology is the study of serums.
Ludwig Tessnow CaseTessnows clothes were tested. The results showed the stains were not dyes, but blood. As a result Ludwig was convicted of murder and executed in 1904.Germany 1901.Ludwig Tessnow was accused of murdering two children. He claimed red stains on his clothes were wood dyes.Paul Uhlenhuth discovered how to test for blood and to distinguish between human and animal blood.
Blood TypingIn 1901 Karl Landsteiner discovered the human blood groups.The difference in blood groups are due to the presence or absence of certain protein molecules called antigens and antibodies.Landsteiner broke the groups into the familiar A, B, AB, and O.
Blood TypeAntigenAntibody%AAB42BBA10ABA & BNone4ONoneA & B44
Blood TypingToday we use:Besides A, B, AB, and O there are over 100 blood factors that can be used to identify a person.Example: RH factorUntil the 1990s scientists used these factors to identify someone.DNA
How much blood do we have?You have about 10 pints of blood pumping through your body.Plasma is the liquid portion of blood and it is 55% of the blood volume.Red blood cells transport oxygen from the lungs and carbon dioxide to the lungs for removal.Antigens on the surface of the RBC give them their blood characteristics.White blood cells produce antibodies to disable and/or destroy invaders.Platelets help to clot blood. The protein fribrin catches red blood cells.
SecretorsAs a general rule, in the U.S. 80% of the population are classified as secretors.
A secretor is defined as a person who secretes their blood type antigens into body fluids and secretions like the saliva in your mouth, sweat, etc.What is a secretor?
Blood at the Crime SceneHemastix will turn from yellow to dark green if blood is present.
Is it blood?We use presumptive tests to answer this question.Hemastix reacts with the hemoglobin in blood.
Blood at the Crime ScenePresumptive Tests (continued)Kastle-Meyer TestA drop of phenolphthalin reagent is added to the sample, and after a few seconds, a drop of hydrogen peroxide is applied to the swab. If the swab turns pink rapidly, it is said to test presumptive positive for blood.
Blood at the Crime ScenePresumptive Tests (continued)Luminol reacts with iron present in blood and a chemical reaction that leads to luminescence revealing the location of the blood.Picks up blood even if diluted up to 10,000 times.
Blood at the Crime SceneFrom what species?Precipitin or Gel Diffusion Blood from mummies 4,000 5,000 years old still give positive results!If its human blood, whose is it? ABO Testing DNA Fingerprinting
Interpreting Blood SpatterBlood spatter can tell us the following:Direction blood droplet was movingWhere the blood droplet came from (area of origin)Type of weapon used in the crime (number or blows)Position of victim, suspects, and objectsSequence of events
Interpreting Blood SpatterThe pointed part of the blood spatter give you the direction the blood was traveling at the point of impact.How to tell the direction that blood droplet was moving.Here is a picture of some blood spatter which hit a surface.
Interpreting Blood SpatterWorking with multiple droplets can tell where the victim was located when the crime was committed.
Angle of ImpactThe angle of impact is useful in determining where blood spatter originated from.
To find the angle of impact:
Sin (angle) = Width / Length
Types of Blood SpatterIrregular spatter pattern indicate higher fall.Passive blood spatter is created by the force of gravity.Height determines diameter of blood spatter.
Types of Blood SpatterProjected blood spatter occurs when energy has been transferred to the blood source. The higher the velocity, the smaller the drops
Low, Medium & High Velocity Falling blood dropsGunshot woundsArterial SpurtingCutting of an arteryExpiratoryBlood from mouth or nose
Types of Blood SpatterContact or Transfer blood spatter occurs when an object with blood on it comes into contact with other objects.WipeSwipe
Surfaces and weapons can affect the blood spatter, therefore, testing of different variables is often done in a case.