Case Study: Whose Side Are They On? The
story of the death of Enrique "Kiki" Camarena, US
Why would Camarena have been killed? He had had
too much success in disrupting drug
Why did the US Gov't bring strong pressure to
bear with regard to this disappearance? Camarena
really was an important DEA agent and knowing the
circumstances of his death would help in the fight
against drug traffickers.
Why do you think FBI forensic geologist Ron Rawalt
suspected as cover-up by the Mexican gov't?
Pictures of the ranch and the bodies must have shown
different types of soil.
Why did agent Rawalt request two soil samples, one
from the body and one from the ranch? He strongly
suspected they would not match, which would indicate the
bodies had actually not been dug up at the Bravo
Section 1.1 Welcome
“Forensic” comes from the Latin,
forensis: “of the forum”, a place of
public debates and trials.
Forensic science is highly interdisciplinary drawing
from geology, physics, psychology, and especially
Section 1.3 Physical Evidence: Matter and its
What is matter? The physical material of the
How is matter relevant to investigations of crime?
You need to understand the properties of matter to
How does matter change between forms? Heat added
or removed brings about phase changes.
Why does heat make phases changes occur? (Have students write down this question and try to answer it on their paper before discussing it. This question should follow discussion of the mechanism of phase changes with adding and removing heat.) Adding
heat increases the random motion of the particles that
make up matter, removing heat reduces this
motion. Increased motion (increased speed) leads to the ability of particles to overcome the attraction between molecules that hold them in place in a solid or in contact in a liquid.
To extend the prior discussion see the activity Modeling the Molecular Level. It should help students to develop mental modeling skills for relating macroscopic events to molecular scale reality.
For the following discussion points a demonstration of a chemical reaction between two solutions that produces a precipitate is useful. Solutions of sodium carbonate and calcium chloride are homogenous mixtures. They react to make insoluble calcium carbonate--a heterogeneous mixture. Finally, the precipitate can be filtered out to show physical separation (possible for mixtures but not for compounds).
According to a chemist what is a pure
substance? It is a substance made of only one
component which cannot be separated into parts by
physical means such as sorting, distillation, filtration,
What is an element? The only kind of pure
substance whose smallest whole unit is an
atom—compounds all require atoms of two or more
different elements bound together.
What is a compound? A substance made of atoms of
two or more elements bound together and in a particular
ratio. The elements in a compound cannot be separated by
physical means but only by chemical reaction.
What is a mixture? Two or more pure substances
physically combined but not chemically bound.
What is a homogeneous mixture? A mixture so well
mixed that an arbitrarily small sample taken from any
part of the mixture will have the same composition as any
other part. Examples: salt or sugar solution, the air we
breathe, an alloy.
What is a heterogeneous mixture? A mixture in
which different parts of have different compositions.
Care must be taken in analyzing the contents of a
heterogeneous mixture so that a representative amount is
See Worked Example 1 on pg. 9 and justify the correct
Section 1.4 The Periodic Table
What is the periodic table? A systematic way to
display information about the elements.
How was the periodic table developed? By 1869
there were 63 known elements. Dmitri Mendeleev was
interested in organizing information about them because
teaching chemistry had become so complicated. There was
not yet a theory for understanding chemistry in a general
way and there were a lot of seemingly unrelated facts to
learn. Mendeleev was able to organize the known elements
by atomic mass in a pattern of repeating (i.e., periodic)
chemical and physical properties. His predictions of
elements not yet discovered made his system famous (even
though others had come up with similar systems
Evidence Analysis, Thin-Layer
Chromatography Optional: Demonstration of
chromatography using colored markers and filter paper.
Wash-able markers and water may work.
Section 1.5 Learning the Language of Chemistry
Some elements have obvious symbols, some do not. Learn to recognize elements by either name or symbol.
(actually from German)
See Worked Example 2 and 3 on pp. 13 and 14 and justify the correct choices.
What are metals and where can they be found on the periodic table? Metals make up most of the table and are found on the left and in the middle. They are generally solids with high to very high melting points. They are good conductors of heat and electricity. Metallic bonds between atoms of metals have the characteristic that electrons can move easily from atom to atom in a ‘sea of electrons’.
What are nonmetals and where can they be found on the periodic table? Nonmetals are found on the right side of the table and are poor conductors of heat and electricity and have (generally) lower melting points. Some are a liquid and many are gases. Interesting exception: carbon is a conductor of electricity, especially in the form of graphite.
What are metalloids and where can they be found on the periodic table? Elements with properties intermediate between metals and nonmetals. B, Si, Ge, As, Sb, Te, Po, and At.
What are chemical formulas and why are they used? They are a shortened means of communicating about compounds using atomic symbols and subscripts that indicate the ratio of the elements found in the compound. They simplify the writing process.
See Worked Examples 4, 5 and 6 on pp. 15 and 16 and justify the correct choices.
Allow students to color periodic tables to match the table found here.
Section 1.6 The Most Important Skill of a Forensic Scientist: Observation
Read the quote by Paul L. Kirk from Crime Investigation very carefully aloud in class. To what is he contrasting physical evidence in this quote? Eyewitness testimony. What are the advantages of pursuing physical evidence in the investigation of a crime? What are the limitations of physical evidence in crime investigation?
Section 1.7 Critical Thinking and the Crime Scene: The Scientific Method
What is the scientific method? A system of methodical problem solving. Construct a model on the board during class through discussion, perhaps in small groups who report to the class their conclusions. Another round might be had using problems similar to that outlined in Worked Example 7 on pg. 18.
Case Study Finale: Whose Side Are They On? The
story of the death of Enrique "Kiki" Camarena, US
What did Rawalt find when he compared the soil sample from Camarena’s body to the soil from the Bravo Ranch? It was clearly not the same (details on pg. 19).
What did Rawalt have to do to prove that the soil on Camarena’s body came from Jalisco State Park, as indicated by his research into the scientific literature? He had to travel there to take a sample and show that it matches the soil from the body.
What were the consequences of this investigation into soil types? Conviction of Mexican officials for conspiracy, identification and conviction of the drug family members responsible for Camarena’s death.
Practice, practice, practice!
Use the resources in the chapter, your peers, and your teacher to fully understand the material.