Introduction

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Introduction

  1. 1. Forensic Chemical Analysis FSC 444Introduction to Forensic Analysis and Analysis of Color
  2. 2. Text reading: Chapter 1, also xv-xviiiQuote from textbook (page xv):“If this is your first course in chemistry, get outwhile you still can!”True, you should have taken General Chemistry– that’s a prerequisite.The book preface also says that you should havetaken organic chemistry, but we will not becovering the sections that require this.So you need not have taken organic.
  3. 3. About this course:This is an analytical chemistry class with focus ontechniques used in forensic science.Q: If you have a B.S. in Chemistry, you presumablytook analytical chemistry, so why do we requireyou to take this course?A: Forensic science is all about analysis, so somerepetition in analytical chemistry is a good thing.And unless you took a forensic chemical analysisclass, at least some of the methods in this class willlikely be new.We will also do several case studies.
  4. 4. LaboratoryMost of the material in the online portion of thiscourse will be “lecture” material that serves tosupport the experiments done in the laboratory.The associated reading in the textbook is listed inthe syllabus.To some extent, more direct notes about thelaboratory will also be included here. These willaim to clarify procedures to be done in lab, explainthe purpose for steps, and go through associatedcalculations.
  5. 5. Laboratory ReportsThe lab reports in this course will likely differ fromwhat you are used to in chemistry classes.The narrative portion of the reports for this classshould be concise, containing only the results –without all the details of how the results wereobtained.Why?When a forensic scientist submits a report to beused in court, the report needs to be concise andunderstandable by non-scientists.Reports in this class, in general, should beprepared with the same goal.
  6. 6. Laboratory ReportsCourtroom lab reports do still need to include thedetails, but these are often provided asappendices.Likewise, our reports will contain all notes writtenduring the lab, appearing after the narrative.These notes will be written on loose sheets of notepaper that will be available in the lab.Finally, the reports will also include answers toprelab and postlab questions. In general, allprelab and postlab questions in the lab manualshould be answered, though occasionalsubstitutions will be made.
  7. 7. Laboratory ReportsSo – you will not need a notebook for this course.You may find use from time to time for a digitalcamera. The one in your cell phone may befine, and if you don’t have one, you can borrowmine or one from another student.In several experiments (those involvinginstruments), it will also be convenient for you tohave a USB flash drive to save your data files. Inweek 2, you can also take your color perceptiontest results with you.
  8. 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 courtsystem, and today “forensic” as an adjectivemeans the legal aspects of the word that follows.“Forensic science” is science – often analyticalchemistry – applied to the law.
  9. 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. 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. 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. 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. 13. Goals of forensic analysis:• Identification (cocaine, wool, dog hair)• Classification (Shetland wool, poodle dog hair)• Individualization (hair from this dog)
  14. 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. 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. 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. 17. Forensic MindsetTo 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 persistentThe “as needed” is very important. A case that usesstandard and certified methods is muchstronger, unless these methods are inappropriatefor some reason.
  18. 18. End ofIntroduction to Forensic Science Go on to Analysis of Color
  19. 19. Analysis of Color (Bell 11.1, 5-5.1)

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