2. Text reading: Chapter 1, also xv-xviii
Quote from textbook (page xv):
“If this is your first course in chemistry, get out
while you still can!”
True, you should have taken General Chemistry
– that’s a prerequisite.
The book preface also says that you should have
taken organic chemistry, but we will not be
covering the sections that require this.
So you need not have taken organic.
3. About this course:
This is an analytical chemistry class with focus on
techniques used in forensic science.
Q: If you have a B.S. in Chemistry, you presumably
took analytical chemistry, so why do we require
you to take this course?
A: Forensic science is all about analysis, so some
repetition in analytical chemistry is a good thing.
And unless you took a forensic chemical analysis
class, at least some of the methods in this class will
likely be new.
We will also do several case studies.
4. Laboratory
Most of the material in the online portion of this
course will be “lecture” material that serves to
support the experiments done in the laboratory.
The associated reading in the textbook is listed in
the syllabus.
To some extent, more direct notes about the
laboratory will also be included here. These will
aim to clarify procedures to be done in lab, explain
the purpose for steps, and go through associated
calculations.
5. Laboratory Reports
The lab reports in this course will likely differ from
what you are used to in chemistry classes.
The narrative portion of the reports for this class
should be concise, containing only the results –
without all the details of how the results were
obtained.
Why?
When a forensic scientist submits a report to be
used in court, the report needs to be concise and
understandable by non-scientists.
Reports in this class, in general, should be
prepared with the same goal.
6. Laboratory Reports
Courtroom lab reports do still need to include the
details, but these are often provided as
appendices.
Likewise, our reports will contain all notes written
during the lab, appearing after the narrative.
These notes will be written on loose sheets of note
paper that will be available in the lab.
Finally, the reports will also include answers to
prelab and postlab questions. In general, all
prelab and postlab questions in the lab manual
should be answered, though occasional
substitutions will be made.
7. Laboratory Reports
So – you will not need a notebook for this course.
You may find use from time to time for a digital
camera. The one in your cell phone may be
fine, and if you don’t have one, you can borrow
mine or one from another student.
In several experiments (those involving
instruments), it will also be convenient for you to
have a USB flash drive to save your data files. In
week 2, you can also take your color perception
test results with you.
8. Introduction to Forensic Analysis (Bell Ch. 1)
Q: What is the origin of the word “forensic”?
A: Click here to find out.
“Forensic” comes from “forum” and meant roughly
“public presentation”.
The Roman forum was a precursor to our court
system, and today “forensic” as an adjective
means the legal aspects of the word that follows.
“Forensic science” is science – often analytical
chemistry – applied to the law.
9. Q: What is the goal of a forensic chemist’s tests?
A: That depends on the evidence. But the goals
are typically both qualitative and quantitative.
Qualitative: Does this white powder contain
cocaine? What else does it contain?
Quantitative: How much cocaine is in the sample?
Questions can also be comparative: Does this
cocaine match that taken in last week’s bust?
10. Q: Cocaine is an organic compound. How can one
hope to compare different samples – shouldn’t
they all be the same?
A: No, cocaine can be pure but is usually mixed
with cutting agents:
diluents (starch, baking soda, etc.)
adulterants (other drugs, like caffeine)
impurities (from source or processing)
So a given batch of cocaine has a “fingerprint”
defined by the percentages of all components!
I asked a forensic chemist at the Onondaga County crime
lab how often they analyze for the other
components, and he said almost never. They usually
need only measure the amount of the illegal
11. Forensic science uses many comparison tests:
• Ballistics (done on a comparison microscope)
• Hair, fibers
• Glass
• Handwriting analysis
• DNA
• Etc.
The usual point of forensic comparisons is to be
able to say whether two samples, typically one
from a crime scene and the other from a
suspect or victim, have the same source.
Q: What are the possible answers to the same
source question?
A: Yes, no, or maybe.
12. Q: Maybe?? Does a forensic scientist on the stand
ever say “maybe”?
A: Well, “maybe” is not the best word to use in
court.
Better: “is consistent with”
Even better, if possible: “is consistent with, and
95% of the population is excluded”
“Excluded” is the same as “no”. “The suspect is
excluded as the source of ______.”
“Yes” is rarely possible. “Consistent” with a high
probability is usually the best one can do.
13. Goals of forensic analysis:
• Identification (cocaine, wool, dog hair)
• Classification (Shetland wool, poodle dog hair)
• Individualization (hair from this dog)
14. By definition, forensic science involves the
interaction between Science and The Law.
This interaction is not always smooth and has built-
in tensions.
Science, by its nature, involves uncertainty, while
the law seeks certainty (beyond a reasonable
doubt for a criminal case).
Scientist strive to understand a situation, while the
law must reach a decision – even if
understanding is not attainable.
So rules of the court impact the way forensic
scientists must work.
15. Rules of the court:
• Admissibility – only accepted (Frye) or
compelling (Daubert) methods are admissible.
• Chain of custody – the scientific results are
meaningless if there is any real or perceived
chance of tampering.
(This is why the Onondaga County Center for
Forensic Sciences does not provide tours!)
• Certification – of scientists and of methods.
• Preservation of evidence – for second opinion
or appeal. A small sample cannot be used up
in the analysis.
16. Q: Which type of evidence is better, circumstantial
or direct?
A: Most will say direct, but it really depends!
Direct evidence usually means that an eyewitness
can say the suspect was at the scene. But
eyewitnesses are known to make mistakes, even
if they say they are sure. Project Innocence data
suggests this is the most common reason for
wrongful convictions.
All forensic evidence is circumstantial – an
inference must be made concerning the meaning
relative to innocence or guilt. But the result and
the inference can be very strong! (For
example, DNA of suspect found under victims
17. Forensic Mindset
To be effective, a forensic scientist must have an
appropriate mindset:
• Assume nothing
• Use all available tools (as needed; this includes
unfamiliar tools in other fields)
• Be creative (as needed)
• Consult others
• Be persistent
The “as needed” is very important. A case that uses
standard and certified methods is much
stronger, unless these methods are inappropriate
for some reason.
