BASIC LABORATORY EXERCISES FOR FORENSIC SCIENCE:

i Instructor’s Manual for Criminalistics An Introduction to Forensic Science 12th Edition Richard Saferstein 1 / 4

ix

BASIC LABORATORY EXERCISES FOR FORENSIC SCIENCE:

AIDS, HELPFUL HINTS, AND ANSWERS

Exercise 2: Crime Scene Investigation and Deductive Reasoning

• What is the timeline of events surrounding Professor Kline’s disappearance and death?

Friday—May 11:

5:15 P.M. Professor Kline leaves his office for a weekend meeting with Dr. Myers.5:45 P.M. Professor Kline meets Dr. Myers and Emily at the Jacobs Falls dig site.7:54 P.M. Sunset. Professor Kline is strangled to death with the fly line from his tent sometime after sunset.

• What is the earliest possible time/date of Professor Kline’s death?

Friday evening after sunset is the earliest possible time of the Professor’s murder.

• Who do you think had the means to commit the crime? Who knows what sort of person is

capable of murder?Emily’s alibi is suspect in the sense that, just because she has hotel receipts and seminar materials, this does not prove attendance. On that theme, her hotel receipt indicates double occupancy. In addition, the e-mail Emily received from Dr. Myers was received after you and Stransky began questioning her! If the e-mail was genuine, she could not have known about it when she claimed she did. Emily had access to Dr. Myers’s computer, so she must have composed it and sent it to herself after she offered it to you as evidence. This explains why Mrs.Myers’s first name is misspelled in the text of the e-mail (either in her haste or ignorance)—Dr.Myers did not misspell his own wife’s name! The significance of this is not readily apparent.Mrs. Myers could be a resentful, disdainful woman who feels she may be better off alone, but her seemingly genuine grief seems to mitigate this level of suspicion.

• Who had a motive?

There is no clear motive spelled out by witness statements or physical evidence. One might consider what Dr. Myers’s reaction would be if Professor Kline had reacted unfavorably to the legitimacy of his archaeological findings, but this is speculation because we have no opportunity to question Dr. Myers directly.More speculation might include Emily’s motives; she may not be as innocent as she wishes to appear. Perhaps she wants to claim this “big find” for herself!The environmentalist was clearly upset to learn about Dr. Myers’s dig and may have felt justified in using any means necessary to defend his cause. Additionally, his alibi is questionable.

• What, if any, further information would help you with this case?

Answers will vary. If needed, direct students’ discussion to the investigative data that can be

gleaned from the following:

• An autopsy report, which may explain the cause of death.
• Toxicology reports, which may reveal if the deceased was poisoned or

drugged.

• X-rays of the body, which may show bullets. These wounds were not

visible externally due to advanced decay.

• Trace evidence analysis of Dr. Myers’s Jeep, recovered at the scene. 2 / 4

x

• Analyses of the additional evidence found in the dumpster behind Emily’s

apartment.

Exercise 4: Forensic Glass Analysis

Exercise I: Procedure Part 8

How close did you come to calculating the known density of aluminum (2.70 g/cc)?

Responses will vary. This is a good opportunity to discuss the concepts of percent error and sampling variability. There is no way to produce a duplicate measurement of exactly the same magnitude every time. This necessitates the practice of multiple measurements to determine an average of the values.

Exercise II: Comparing Glass Density

Preparation of the sodium polytungstate (SPT) solution (density 5 2.80 g/mL). Visit the Sometu company website for product information.

Time: Approximately 30 minutes

Note: Do not use metal in the preparation or storage of this solution.

• Set up a 250 mL plastic beaker with a magnetic stir bar.
• Add 36.0 mL distilled or deionized water to the beaker.
• Measure 164.0 g SPT powder (Na6 (H2W12O40)•H2O).
• While stirring gently, gradually add the SPT powder to the water. Allow

the SPT to completely dissolve before making further additions. Never add water to the SPT, as an insoluble clump will form.

• Seal tightly and store at room temperature in a plastic or glass container.
• Transfer to a dropper bottle or aliquot into sealable containers and provide

a plastic (disposable) transfer pipette for student use.

• Be sure to test all glass fragments beforehand to determine how much SPT

solution will be needed for each assay. It may be helpful to guide students by informing them of this amount before they begin.

Exercise 6: The Microscope

Exercise I: The Compound Microscope

Is the letter “e” right-side-up? Is the “e” still right-side-up?

The orientation of the letter “e” when viewed through the lens of a compound microscope should be upside-down relative to its orientation when viewed by the naked eye. In addition, when the stage is moved to the right, the image in the eyepiece should move to the left.

Exercise II: The Stereomicroscope

• / 4

xi

Part II—Examination of Typeface

Is the “e” still right-side-up?

The image of the object as viewed through the eyepiece should appear in the same orientation as it is on the stage.

Part III—Examination of Nails

• Are all five nails exactly the same shape?

Your students should recognize that each nail is unique in some way, even if they appear identical to the naked eye.

• Is each head the same thickness as the others?

Answers will vary.

• Are they all the same length?

Answers will vary.

• Do the striations appear to be identical?

Answers will vary.

• Is there a particular shape or mark that occurs on each nail that has no bearing on the

quality or performance of the product?Answers will vary.

Exercise 7: Forensic Hair Analysis

Exercise I: Casting Scale Patterns

• Compare this to the actual hair—which is a better image for viewing the scale pattern?

The cast is preferred to the actual hair for examination of the scale pattern on the surface of a hair.

Exercise 8: Handwriting Comparison

Exercise I

Part I—Example 1

The letters on the left are from the forgery. Examples of Howard Hughes’s known handwriting are on the right. Point out the differences between the two using specific examples.Many letter forms do not match Hughes’s writing. For example, the “i” dots and “t” crossings are incorrectly formed. Hughes normally signed his middle initial “R” with one stroke. The forgery has a two-stroke “R.”

Part I—Example 3

• / 4