Forensic Science Unit 3.1: DNA Profiling
My learning objectives:
(9) The student analyzes blood spatter at a simulated crime scene. The student is expected to:
(A) analyze blood stain patterns based on source, direction, and angle of trajectory; and
(B) explain the method of chemically isolating an invisible blood stain using reagents such as luminol.
(11) The student explores serology laboratory procedures in forensic science. The student is expected to:
(A) explain forensic laboratory procedures to determine if a stain detected in a crime scene is blood;
(B) identify the red blood cell antigens and antibodies as they relate to human blood types;
(C) determine genotypes and phenotypes in the human red blood cell system using Punnet Squares; and
(D) research methodologies used to collect and analyze other body fluids.
(3) The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions
within and outside the classroom. The student is expected to:
(F) research and describe the history of science and contributions of scientists.
(4) The student explores the history, legal responsibilities, and career options for forensic science. The student
is expected to:
(E) recognize the major contributors to the development of forensic science; and
(F) illustrate the history of forensic science.
Objectives for the Unit
Conceptual
Describe how blood circulates through arteries, veins, and capillaries
while being pumped by the heart.
Describe the composition of blood.
Explain how oxygen is carried or transported by a red blood cell.
Describe two different functions of white blood cells.
Describe the role of platelets.
Describe the function of the immune system.
Explain how white blood cells are the main "players" in the immune system.
Compare and contrast antigen and antibody.
Describe an antigen-antibody reaction, and explain how an antibody
identifies an antigen.
Describe the effect of antibodies on an antigen
List three different antigens found on red blood cells.
Distinguish between the following blood types:
A+ and A-, B+ and B-, AB+ and AB-, O+ and ODescribe how to determine someone's blood type.
Analyze the results of blood typing to determine someone's blood type.
Explain why blood types provide class evidence and not individual evidence.
Distinguish between spines and satellites in blood spatter.
Devise an experiment to determine the effect on the blood spatter
of blood being dropped:
a. From different heights
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b. Onto different surfaces
c. From different angles
Using the terms cohesion and gravity, explain why a drop ofblood
will be circular in appearance as it drops.
Using the terms cohesion and surface tension, explain why blood will
appear as a rounded surface when it lands on flat surface
Using the terms momentum and cohesion, explain why most of the
blood will remain as a drop where it first strikes a surface, but some of
the blood will continue to move forward, forming an elongated
"spine."
Given a number of blood-spatter stains; be able to determine the
direction that the blood was moving. Include in your answer the shape
of the blood spatter and the terms satellite and blood spatter.
Distinguish between the following bloodstain patterns:
a. Cast off
b. Transfer
c. Shadowing, or void
Distinguish between a swipe and a wipe bloodstain pattern.
Describe the forensic significance of identifying the type of blood spatter
found at a crime scene.
Explain the blood spatter pattern called an arterial gush. Include in
your answer the following:
a. The overall pattern of the blood spray
b. The reason the pattern shows high points and low points.
Describe the difference in a blood spatter pattern if blood was
dropped from a height of 30 cm vs. 100 cm.
Define the term terminal velocity.
Explain the relationship of terminal velocity to the size of a
droplet of blood as it is dropped from different heights ranging
from 50 cm to 100 cm to 300 cm.
Given two blood spatter patterns, to be able to distinguish a difference
between high-velocity blood spatter size(gunshot wound) versus lowvelocity blood spatter size (blunt-force trauma).
Given two blood spatter patterns, to be able to determine which
came from a gun fired at close range and which came from a gun
fired from a distance.
Draw lines of convergence lines to determine the source of blood.
Distinguish between lines of convergence and area of convergence
Explain how to draw lines of convergence from several drops of blood
in order to determine the area of convergence or source of blood.
Include in your answer:
a. How to determine the direction or movement of the blood
b. Where to begin drawing your line in reference to the main blood
droplet and the satellite blood drops.
c. How should the line be drawn through the main droplet of bloodstain?
d. How far to draw your lines
e. How to determine the area of convergence using these
lines of convergence.
f. How to draw a circle around the area of convergence.
Define angle of impact for blood spatter.
a. How is angle of impact used in forensic blood spatter analysis?
b. How does the angle of impact affect the shape of blood spatter?
Describe how to recognize if a blood drop was dropped straight
down (90 degree drop) based upon the shape of the drop at
impact.
Explain what happens to the shape of a blood spatter as you move from a
10- degree impact angle to a 60-degree impact angle.
Explain how to calculate the impact angle from a single droplet of blood.
Differentiate between the area of convergence and the area of origin of
blood.
Estimate the area of origin using the tangent method.
a. Find the area of convergence.
b. Calculate the impact angle from a single drop of blood.
c. Measure the distance from the leading edge of blood to the center
of the area of convergence.
d. Applying the law of tangents to estimate the area of origin.
Given several drops of blood, to be able to analyze the crime scene by
conducting a blood-spatter analysis:
a. Determine the direction of motion of the blood.
b. Determine the area of convergence of the blood
droplets. c. Determine angle of impact for several drops
of blood.
d. Calculate the area of origin for the blood droplets using the protractor
method or by applying the law of tangents.
Use blood-spatter analysis to try to recreate the events of the crime.
Determine if an eyewitness's account of what happened at the crime
scene is consistent with the blood-spatter evidence.
Describe different tests used to screen for the presence of blood.
Describe how Luminol can help to reveal blood spatter. Include
in your answer:
a. What is Luminol?
b. How is it applied?
c. What part of the blood reacts with Luminol?
d. What type of light is needed to view evidence based upon Luminol?.
Describe antibody testing done to determine if blood is from a human
or non-human source.
Laboratory
A presumptive test for blood
Effect of Height on blood drops
Area of Convergence
Blood Droplet Impact Angle
Area of Origin