FORENSIC SCIENCE

WHAT IS FORENSIC SCIENCE?

WHAT IS FORENSIC SCIENCE? Forensic scientists collect, preserve, and analyse scientific evidence during the course of an investigation. While some forensic scientists travel to the scene to collect the evidence themselves, others occupy a purely laboratory role, performing analysis on objects

FORENSIC SCIENTISTS INVESTIGATE THE DETAILS OF A CRIME SCENE

BLOOD SPATTER A FEW FACTS ABOUT BLOOD… What are the components of blood? Why is blood so important? What can blood tell us about a crime scene?

WHAT ARE THE COMPONENTS OF BLOOD? FYI: An average body contains 0.2 mg of gold, which is in our blood

1. RED BLOOD CELLS RBC AKA: Erythrocytes 45% of the volume Hemoglobin: protein that carries oxygen to all tissues of the body and carbon dioxide away from tissue and back to the lungs (RESPIRATION) It takes about 30 seconds for a RBC to make a complete trip around your body

2. WHITE BLOOD CELLS WBC AKA: Leukocytes 1 WBC to every 700 RBC Defend against infections by surrounding and engulfing (eating) the bacteria

3. PLATELETS AKA: Thrombocytes 1 platelet to every 20 RBC Gather @ bleeding site and clump together to seal off a wound 3. PLATELETS

4. PLASMA “watery” liquid part of the blood The RBC, WBC, and platelets are floating in this Makes up 55% of the total volume Made of water, salt (electrolytes), and protein FYI: Coconut water can be used (in extreme emergencies) as a substitute for blood plasma

FUN BLOOD FACTS: The average human body holds about 1.25 gallons of blood (if you weigh 160 lbs) The heart pumps 2,000 gallons of blood through it every day (recycled of course) It would take 1.2 million female mosquitos all sucking at once to drain the body of blood. Male mosquitos are vegetarian.

THE GENETICS OF BLOOD THERE ARE THREE ALLELES FOR BLOOD TYPE: A, B, O THERE IS A SEPARATE ALLELE FOR THE RH FACTOR, OR RHESUS FACTOR (RH +/-) YOU INHERIT THESE ALLELES FROM YOUR PARENTS, ONE FROM EACH (2 TOTAL) TYPE A AND B ARE CODOMINANT AND O IS RECESSIVE TO A AND B BLOOD TYPING IS A QUICK AND EASY WAY TO RULE-OUT SUSPECTS OF A CRIME

it makes no surface molecules at all. NO antigen. There are antigens on your RBC! An antigen is a molecule capable of inducing an immune response The A allele codes for an enzyme that makes the A antigen, The B allele codes for an enzyme that makes the B antigen. The O allele codes for a protein that is not functional; it makes no surface molecules at all. NO antigen. Antigens are like the sprinkles on a donut...except they are A or B antigens on a RBC. There are no sprinkles on the RBC if you have type O blood.

The Rhesus Factor AKA: Rh factor This is an antigen that exists on the surface of red blood cells in most people. People who have the Rhesus factor are considered to have a positive (+) blood type, such as A+ or B+. Those who don't are considered to have a negative (-) blood type, such as O- or AB- Universal donor = can donate to every other type of blood

There are two antigens, A and B. A antigen on the RBC = Type A blood B antigen on the RBC = Type B blood Both A and B antigens are present = Type AB blood Neither antigen present = Type O blood A + O = B + O = A + B = O + O =

NOW, WE GET TO EXPERIMENT ON TYPING BLOOD!

What does blood type have to do with forensic science?

What do your results infer? What should investigators do next?

Day 2: Forensic Science of Blood Spatter

ANALYZING BLOOD SPATTERS What does the shape of the drop tell us?

3 Types of Blood Evidence Drip/Passive Gravity pulls it down Round and flat...no tails Transferred Smeared from a hand or other object Spatter High, medium, low velocity

EXPERIMENT WITH MAKING DIFFERENT BLOOD SPATTERS