STP 15: Chemistry and Crime
Test 1
January 20, 1998

Multiple choice, 3 points each:


1. The effectiveness of an expert's testimony is almost always dependent on
  1. the experience of the expert.
  2. the ability of the expert to talk in clear, concise language.
  3. the educational background of the expert.
  4. the scientific validity of the tests used.
  5. all of the above.

2. Evidence having class characteristics can
  1. exonerate an innocent suspect.
  2. link a person to a crime with a high degree of certainty.
  3. always be fitted together in the manner of a jigsaw puzzle.
  4. have no evidential value.

3. A technique frequently used to compare soils is
  1. the immersion method
  2. density gradient tubes.
  3. flotation.
  4. Becke Line.
  5. dispersion.

4. A compound can tentatively be identified with gas chromatography from its
  1. carrier gas.
  2. Rf value.
  3. partition coefficient.
  4. retention time.
  5. peak height.

5. In neutron activation analysis, an element is identified by measuring the energy and intensity of emitted
  1. protons.
  2. electrons.
  3. neutrons.
  4. gamma rays.
  5. alpha rays.

6. The most important tool of the firearms examiner, who analyzes fired bullets, is the
  1. compound microscope.
  2. comparison microscope.
  3. stereoscopic microscope.
  4. polarizing microscope.
  5. scanning electron microscope.

7. A human head hair is most readily characterized by
  1. the absence of a cortex.
  2. its scale pattern.
  3. a medulla that is more than the overall diameter of the hair shaft.
  4. a medulla that is absent or is less than 1/3 the overall diameter of the hair shaft.
  5. a continuous or interrupted medulla.

Short answer questions:


8. List the three primary functions of a forensic scientist. (6 points)

9. In cooperation with the medical examiner or coroner, what type of evidence is to be retrieved from a deceased victim for examination in the crime laboratory? List at least three types of evidence. (6 points)

10. What are the two methods for analyzing glass? Name both methods, indicating what property is determined by each. Explain one of these two methods, describing how the test is carried out. (10 points)

11. Describe how thin layer chromatography works, identifying the mobile and stationary phases. What advantages and disadvantages does TLC have compared to other types of chromatography? (10 points)

12. Emission spectroscopy and x-ray diffraction share two disadvantages relative to atomic absorption spectrophotometry and neutron activation analysis. What are these disadvantages, and why are they so important? (6 points)

13. How does a scanning electron microscope provide visual images? How does this type of microscope also provide chemical information? (9 points)

14. Fibers are difficult to analyze by traditional chemical means, due to the small sample size. Describe how the dyes in a fiber may be analyzed in a non-destructive manner. (Explain briefly how the method works.) (8 points)

15. The binder in paint is an organic compound which is more difficult to analyze because it is a polymer. Describe the chromatographic method for analyzing paint binders, explaining how it differs from other types of chromatography. (8 points)

Essay

16. For this essay question, write your answer in complete sentences, using proper grammar. Describe the crimes that Bobby Joe Long was accused of. How did investigators learn about Long? What features of these crimes led investigators to suspect a serial murderer was involved? What laboratory tests were used to analyze the physical evidence in these cases? (16 points)