Unit 1.1: Investigating the Scene Review Principles of the Biomedical Sciences

What is Biomedical Science? What is Forensic Science?

Biomedical Science: The application of the principles of the natural sciences, especially biology and physiology, to clinical medicine. Forensic Science: The application of scientific knowledge to questions of civil and criminal law. Principles of biomedical science can be used to investigate the circumstances surrounding a mysterious death.

Essential Question #1: What can be done at a scene of a mysterious death to help reconstruct what happened?

Interview witnesses, possible suspects, and known associates. Examine the crime scene for all evidence in an orderly fashion… different search methods. Sketch the crime scene using a key and scale. Photograph the scene with rulers for size estimation. Collect and document all physical evidence.

Essential Question #2: How do the clues found at a scene of a mysterious death help investigators determine what might have occurred and help identify or exonerate potential suspects?

Blood Type Blood typing is more often used to eliminate suspects. Just because a suspect has the same blood type found at a crime scene this does not mean that it is their blood. There are four basic blood types: Type A – has A antigens Type B – has B antigens Type AB – has A and B antigens Type O – has no antigens Blood types can be found by adding antibodies to the blood and seeing if the blood clumps. Blood will clumps due to the antibody binding to the antigen. Antibodies are specific to each antigen so only B antibodies will bind with B antigens. Lets look at this animation: http://waynesword.palomar.edu/aniblood.htm Antigens are protein molecules on the surface of RBCs. Antibodies circulate in the liquid portion of the blood, plasma.

Blood Type Blood Type Anti-A Serum Anti-B Serum O - (no clumping) A AB Type O does not clump with either antibody because it contains no antigens. Type A clumps only in the presence of A antibodies because it only has A antigens. Type B clumps only in the presence of B antibodies because it only has B antigens. Type AB clumps in the presence of both antibodies because it has both antigens. In order to further determine identity DNA testing must be done.

Fingerprints No two people have the same prints. There are three main patterns you need to understand: Loop Whorl Arch More Info on Identifying these patterns can be found at: http://www.youtube.com/watch?v=I rpTqKkgygA Not even identical twins Form before you are born and remain unchanged during a person’s lifetime.

Fingerprints In order to identify a fingerprint scientists must match minutiae (specific ridge marks) between the crime scene and suspects. Match at least 12-15 points of similarity between the two prints to establish that they are identical.

Hair Cannot pinpoint a suspect with 100% certainty but it can help eliminate persons of interest and provide clues as to who might have been present at the scene of the crime. At microscopic level: Race, sex, age, origin. Hair is made of keratin, a protein found throughout our integumentary system. It has three layers: Cuticle-Cortex-Medulla Look for distinguishing marks within these three layers. Origin- animal versus human Cuticle- flattened, scale-like cells that overlap one another (humans no repeating pattern, animals repeating pattern) Thickness of cuticle, variation in thickness, presence of pigment, color, nature of outer cuticle margin (smooth, looped, ragged, damaged) Cortex contains pigment granules responsible for hair color- look at organization, density, size, distribution between racial groups and individuals Medulla- continuous, discontinuous, fragmentary, absent Growth stage of hair, diameter, presence of artificial treatment, damage, disease, other hair abnormalities.

Shoe Prints Can help match to a potential suspect. Almost all footwear bear undersoles with distinctive patterns. Individuality can be seen in the general wearing of the shoe. Weight Walk Size

Time of Death Signs to estimate time of death: Rigor mortis – Tightening of the muscles after death. Algor mortis – Internal temperature cooling. Lividity – Blood pooling. Amount of decomposition. Entomology – study of bugs and when they arrive after death. Factors affecting Algor Mortis: Clothing Original internal temperature Ambient temperature Environment Body size

Essential Question #3: How do scientists design experiments to find the most accurate answer to the question they are asking? Example Experiment: A scientist is studying the affect caffeine on blood sugar in diabetics. The scientist gathers 300 diabetics and half of them drink caffeine every day. The other half do not drink caffeine. They continue this for a month. Blood sugar is measured every day.

Experimental Design Problem: Specific and measureable question you are trying to answer. Hypothesis: Clear prediction of the anticipated results of an experiment. Independent Variable: The variable that is varied or manipulated by the researcher. Dependent Variable: The measurable effect, outcome, or response in which the research is interested.

Experimental Design Experiment: A research study conducted to determine the effect that one variable has upon another variable. Procedure Safety concerns, materials used, multiple trials Personal Protective Equipment: Specialized clothing or equipment, worn by an employee for protection against infectious materials (as defined by OSHA). Reliable & Valid Random- Patients should be selected at random. Replication- How many times the experiment is repeated? Standardization- Each group should have the same conditions as each other except for the independent variable. All extraneous variables should be controlled and kept constant between groups. The experimenter chose people with diabetes at random Repeated- there were 150 participants in each sample. Each group should have the same type of diabetes, same diet, and same physical activity.

Experimental Design Control Group: The group in an experiment where the independent variable being tested is not applied so that it may serve as a standard for comparison against the experimental group where the independent variable is applied. Positive Control: Group expected to have a positive result, allowing the researcher to show that the experimental set up was capable of producing results. Negative Control: Control group where conditions produce a negative outcome. Negative control groups help identify outside influences which may be present that were not accounted for when the procedure was created.

Experimental Design Analyze Data and Observations/Graphs Draw Conclusions Discuss any possible sources of error

Essential Question #4: How are bloodstain patterns left at a crime scene used to help investigators establish the events that took place during a crime?

Blood Spatter Analysis Helps establish the events that took place; help distinguish between an accident and foul play. Things that affect blood spatter patterns: Force Height Amount of blood Angle Objects in the way How close the victim is to the perpetrator