Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Forensic chemistry introduction

Related Books

Free with a 30 day trial from Scribd

See all
  • Be the first to comment

Forensic chemistry introduction

  1. 1. Do Now Withyour partner list as many types of forensic evidence as you can  Think of all those CSI’s and L&O’s you’ve watched!  Team with longest list gets bonus points!
  2. 2. Forensic Science An Introduction
  3. 3. What is forensic science? Science in service to the law  “…the application of science to those criminal and civil laws that are enforced by police agencies in the criminal justice system.” Saferstein
  4. 4. What’s the key concept in FS? Locard’s Exchange Principle (~1910)  Whenever a criminal comes in contact with a person or object there is a cross-transfer of evidence.
  5. 5. What are the consequences ofLocard’s Exchange Principle?  The perpetrator leaves evidence behind and also takes evidence away  The longer you wait before collecting evidence the less there is left  Every person at the crime scene including police investigators will contaminate it
  6. 6. Realistic?
  7. 7. What is Forensic Science Trying to Do? The goal of Forensic Chemistry is to determine the provenance of a sample.  Link it to a person, place or thingprov·e·nance Pronunciation: präv-n&n(t)s, prä-v&-"nän(t)s Function: noun Etymology: French, from provenir to come forth, originate, from Latin provenire, from pro- forth + venire to come -- more at PRO-, COME 1 : ORIGIN, SOURCE 2 : the history of ownership of a valued object or work of art or literature
  8. 8. The Crime Lab Physical Science Firearms Biology Photography DocumentsPathologist Crime Odontologist Lab Voiceprint Polygraph Analysis Latent Toxicology Evidence Engineer Fingerprints Psychiatrist Collection Anthropologist Entomologist
  9. 9. Activity Time! Assign each of the items in your evidence list to the proper department in the crime lab Feel free to add more types of evidence Populate your crime lab with your favorite TV characters
  10. 10. Anthrax Letters 5 dead 17 sickenedWhat types of evidence would you look for?
  11. 11. Anthrax Letters Trace hair and fibers in envelope Ink analysis may reveal manufacturer DNA from stamp or envelope seal Cellophane tape ends match over four letters Paper examination may identify manufacturer Fingerprints Photocopier toner may reveal manufacturer Handwriting analysis shows four letters written by same person Indented writing Bar codes for mail handling
  12. 12. Analytic vs. Forensic Chemistry SimilaritiesAnalytic Forensic Wants to find  Wants to find composition of composition of samples samples  Compounds  Compounds  Proportions in  Proportions in mixtures mixtures Uses same  Uses same instruments as instruments as forensic analytical
  13. 13. Analytic vs. Forensic Chemistry DifferencesAnalytic Forensic Known source  Need to determine Good idea of what the source composition is likely  Little knowledge of to be composition Used for quality  Often complex control mixtures so hard to Well defined samples find appropriate and controls controls
  14. 14. Roles of the Forensic Scientist Analyze physical evidence Provide expert testimony Train evidence collection units in recognition, collection and preservation of evidenceWould you expect to see Gil Grissom collecting evidence at a crime scene?
  15. 15. The Expert Witness An expert witness can testify as to his/her opinion of what the evidence indicates A lay witness can only testify as to fact
  16. 16. The Expert Witness Trial judge must be satisfied that the expert  Has skill or knowledge that will aid the court in determining the truth  Education (degrees, courses)  Training (internship under experienced practitioner)  Experience (years on the job, publications, professional societies) Trial judge is the gatekeeper
  17. 17. The Expert Witness Jury assigns weight to the expert’s opinions Jury looks at  Credentials  Demeanor  Whether material is presented simply and clearly Jury is the trier of fact
  18. 18. And Now for Some Expert Testimony My Cousin Vinny
  19. 19. A Big Driver in the Plot Can the evidence be admitted into court?
  20. 20. Admissibility: A Moving Target Frye v. US (1923)  Scientific evidence is admissible only if it has gained general acceptance in the field  Rejected polygraph opinions Historical Perspective  Tennessee v. John Scopes (1925)  The Monkey Trial
  21. 21. Admissibility: A Moving Target Coppolino v. State of Florida (1968)  Doctor accused of poisoning his wife with succinylcholine chloride  New and unique tests performed specifically for this case  Detected by-products of metabolism of poison (succinic acid)  Admissible if based on scientifically valid principles and techniques
  22. 22. Admissibility: A Moving Target Federal Rule of Evidence 702 (1975)  Approved by Congress  More flexible general relevance test for admissibility of opinion testimony by experts  “If scientific, technical or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact at issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.”
  23. 23. Admissibility: A Moving Target Daubert v. Merrell Dow Pharmaceuticals (1993)  When expert evidence based on “scientific knowledge” is offered at trial, the judge acts as gatekeeper to determine if the evidence is “reliable”  Four suggested factors in determining reliability  Testable using the scientific method  Peer reviewed  Error rates  Acceptability to the scientific community  Trial judge given lots of flexibility  Muddy waters—what is scientific knowledge?  What about other types of experts?
  24. 24. Admissibility: A Moving Target Why Daubert won on appeal  When Congress passed Rule 702 it ignored the Frye general acceptability criterion  Frye was no longer “good law”--
  25. 25. Admissibility: A Moving Target Kumho Tire Co v. Carmichael (1999)  Daubert factors are extended to non-scientist expert witnesses.  Daubert factors are not the only ones that can be considered  Trial judge now has enormous flexibility
  26. 26. And it’s not settled yet….. Daubert and Kumho apply to federal cases only 18 State Courts have adopted Daubert standards Other State Courts have rejected Daubert and still use a modified Frye standard
  27. 27. What’s driving the growth of FS? Miranda decision  Fewer confessions Increase in drug seizures and arrests  More testing DNA profiling  More testing with sophisticated equipment Other new technologies
  28. 28. Miranda vs. Arizona (1966) Before questioning by the police, suspects must be informed that they have:  The right to remain silent  The right to consult an attorney  If indigent an attorney will be provided for them  Anything they say may be used against them in court Arizona Department of Library Archives and Public Records)
  29. 29. Dickerson Dickerson vs US (2000)  Congress passed law in 1968 saying voluntary confessions are exempt from Miranda  Supreme Court overrules Congress in 2000  Congress can’t overrule the Supreme Court on constitutionally guaranteed rights except by the amendment process
  30. 30. Results of Miranda Confessions are less likely to hold up in court since the burden of proof of Miranda statement lies on police Police and prosecutors rely more independent (scientific) evidence to prove guilt
  31. 31. What is the most common task a forensic scientist performs? Take 5 minutes and discuss this in groups of 4 and then be ready to report out your reasoning.
  32. 32. Crime Wave or Better Enforcement?
  33. 33. Federal Drug Seizures
  34. 34. Arrests by Drug Type
  35. 35. The Economics of Drugs According to the United Nations Office on Drugs and Crime, "[T]he value of the global illicit drug market for the year 2003 was estimated at US$13 bn [billion] at the production level, at $94 bn at the wholesale level (taking seizures into account), and at US$322bn based on retail prices and taking seizures and other losses into account." This is larger than the total economies of 88% of the countries in the world! Source: United Nations Office on Drugs and Crime (UNODC), World Drug Report 2005 (Vienna, Austria: UNODC, June 2005), p. 127.
  36. 36. Average % THC in Marijuana SeizuresRecent seizures in Atlanta had plants with 18% THC content.
  37. 37. The Forensic All Stars Mathieu Orfila (1787-1853)  Father of toxicology Alphonse Bertillon (1853-1914)  First system of personal identification Francis Galton (1822-1911)  Classification of fingerprints Dr. Leon Lattes (1887-1954)  Determination of blood groupings from dried blood stains
  38. 38. The Forensic All Stars Calvin Goddard (1891-1955)  Father of ballistics  Use of comparison microscope Albert S. Osborn (1858-1946)  Fundamental principles of document examination Walter C. McCrone (1916-2002)  Application of microscopy to analytic problems
  39. 39. The Forensic All Stars Hans Gross (1847-1915)  First text detailing application of science to criminal investigation Edmond Locard (1877-1966)  Locard’s Exchange Principle  Thereis an exchange of materials whenever two objects come in contact
  40. 40. What is Science? An organized body of knowledge about nature A method for exploring nature and the order in it A set of tools for solving problems about nature
  41. 41. Coast Guard Drug Seizures