STP 15: Chemistry and Crime

Test 2, February 5, 1998

Multiple choice (2 points each)

1. Electrophoresis of DNA fragments is commonly used in which of the following DNA typing techniques?
(a) PCR (DQ alpha)
(b) RFLP
(d) none of the above

2. Compounds assumed to be accelerants in an arson case are analyzed using which of the following techniques?
(a) IR
(b) TLC
(c) GC
(d) pyrolysis GC

3. This technique is the forensic toxicologist's method of choice for confirming positive results from a drug-screening test.
(a) gc-mass spec
(b) TLC
(c) GC

4. This test method is useful for determining the blood type of dried bloodstains.
(a) precipitin
(b) Kastle-Meyer
(c) adsorption-elution
(d) None of the above. It is impossible to carry out blood typing tests on dried blood.

5. A person with type AB+ blood has which of the following?
(a) A, B, and D antigens but no A, B, or D antibodies
(b) A, B, and D antibodies but no A, B, or D antigens
(c) A, B, and D antigens and possibly A, B, and D antibodies
(d) A, B, and D antigens and definitely A, B, and D antibodies

Short answer:

6. You are analyzing evidence from a fire scene to determine if the fire was intentionally set. The evidence collectors have brought you a paint bucket partially filled with ashes from the fire. How would you analyze this material? (Be specific about sample treatment and methods used.) What additional samples would you need to analyze before coming to a conclusion? How would these other samples be analyzed? (12 points)

7. How are the chemical reactions that occur in bomb explosions different from other oxidations? List at least two differences. (6 points)

8. Enzyme Multiplied Immunoassay Technique (EMIT) is often used for drug testing. Explain how this method indicates the presence of drugs. Since this method gives quantitative results, is confirmation necessary? (9 points)

9. In the Sam Sheppard case, dried bloodstains found in Marilyn Sheppard's bedroom have recently surfaced. It was originally assumed that this blood belonged to Marilyn, since Sam Sheppard had no open wounds. Which type of DNA testing of is most suited to analyzing old samples of this type, which might be degraded? Explain your answer in terms of how the DNA testing methods work. (9 points)

10. Blood alcohol concentrations are often determined by measuring the alcohol content in a person's breath. What assumptions are involved in using this method? (6 points)

11. In a recent case in Missouri, a man was convicted of murdering his wife even though her body was never found. Investigators found the car in which she was killed; blood in the car enabled them to identify her as the victim. The fact that this couple had two children facilitated the identification process. What method was probably used to analyze her blood? Sketch some plausible results from this type of test, and indicate how the analysis of family members' blood confirmed her identity. (12 points)

12. Explain how blood typing tests are carried out. Your explanation should include a description of how the test reagents/solutions are prepared. (12 points)

13. Describe the steps involved in analyzing a urine sample for drugs of abuse. Assume that you will be testing for a variety of abused drugs (for example, barbiturates and narcotics). (9 points)

14. Write your answer in complete sentences, using proper grammar. Describe the crime discussed in the case reading. How did the victim and the suspect know each other? What was unusual about the murder weapon used in this case? What techniques were important in analyzing evidence in this case? (15 points)