Materials Included In Kit

Additional Materials Required

Prelab Preparation

To make 100 milliliters of each of the refrigerator contents and the stomach contents:

1. Label five 250-mL beakers or plastic cups “Catsup,” “Smoothie,” “Clear Liquid,” “Fruit Punch” and “Stomach Contents.”
2. Fill a 500-mL graduated cylinder to the 350-mL mark with distilled water.
3. Add four to five drops of the red food dye.
4. Pour approximately 100 mL of the liquid in the 500-mL beaker into each of the beakers labeled “Catsup,” “Fruit Punch” and “Smoothie” and 50 mL into the beaker labeled “Stomach Contents.”
5. Pour approximately 50 mL of distilled water into the stomach contents beaker and approximately 100 mL of distilled water into the clear liquid beaker.
6. Add 50 mL of methyl cellulose solution into the catsup beaker and 50 mL of methyl cellulose into the smoothie beaker.
7. Add 10 mL of 0.1 M sodium hydroxide to the beakers containing fruit punch, stomach contents, and clear liquid.

To prepare the fibers for fiber analysis:

1. Using scissors, cut the nylon and cotton fabrics into 1-cm squares.
2. The fibers found at the crime scene are cotton fibers—ensure that each group gets two of these squares.

Make 15 copies of the Shoeprint Evidence Sheet and the Fingerprint Evidence Card.

Safety Precautions

Work carefully around candle flames. The “poison” in this lab is a dilute base, sodium hydroxide, which is corrosive to skin and eyes and moderately toxic by ingestion or inhalation. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All liquid wastes from this activity may be disposed of according to Flinn Suggested Disposal Method #26b, down the drain with excess water. All solid wastes from this activity may be disposed of according to Flinn Suggested Disposal Method #26s, in the regular trash.

Lab Hints

• Enough materials are provided in this kit for 30 students working in pairs or for 15 groups of students. This laboratory activity can reasonably be completed in two 50-minute class periods.
• The lab tests should be performed in the order indicated to narrow down the list of suspects.

Teacher Tips

• Place the blood samples in a central location or transfer to a beaker and dispense each with a pipet.
• Instead of making catsup using methyl cellulose and food coloring, real catsup will work just as well.
• The moral of the story is: Do not store chemicals in a refrigerator that is not designated for that purpose.

Answers to Prelab Questions

1. Even though the teachers’ lounge is off limits to students, use your imagination to draw a sketch of what it might look like, including the location of the evidence found.

   Accept all reasonable drawings. Drawings should include a dented refrigerator, broken window with drops of blood and fibers, knocked over toner cartridge, and footprint on a sheet of paper.

2. What should the custodian have done to preserve the crime scene before the authorities arrived that morning?

   The custodian should not touch any items in the teacher’s classroom, including the body. He should also keep people out of the teacher’s classroom. He did not seem to be aware of the evidence in the Teacher’s Lounge.

3. What might have happened to Mr. Mathematics and what evidence is involved?

   Accept all reasonable answers. Someone may have poisoned Mr. Mathematics because it seems that he may have consumed one of the red liquids in the refrigerator.

4. What tests could be conducted to determine the person or persons involved in the crime?

   Answers will vary but may include fiber analysis, blood typing, shoeprint analysis, chemical analysis and fingerprint analysis.

5. Before any tests are conducted, is there any conclusive evidence pointing to the people involved or the possible course of events?

   No.

Sample Data

Part 1. Test for Poison

Was Mr. Mathematics poisoned? If so, what is the most likely substance?

It appears, based on the positive results for poison in his stomach contents, that Mr. Mathematics was poisoned by drinking the fruit punch. The clear liquid on the top shelf also appears to be a poison.

Test 2. Shoe Print Looking at the size of the shoe in the data table, does the shoe evidence point to any one person who may have poisoned Mr. Mathematics? Does it show that someone may not have been involved?

The shoe size evidence does not point to any one person; however, it does show that Lenny Language may not have been involved.

Test 3. Fiber Analysis Looking at the fiber observations from the data tables above, does the fiber evidence point to any one person who may have poisoned Mr. Mathematics? Does it show that someone may not have been involved?

The fiber analysis does not point to any one person; however, it does show that Stanley Student and Lenny Language may not have been involved.

Test 4. Blood Analysis Looking at the blood analysis data in the table above, which suspects may have been involved in the death of Mr. Mathematics? Does the blood analysis show that any suspect would not have been involved?

The blood analysis suggests that either Person V or Person X may have been involved in the death of Mr. Mathematics. It suggests that Person W, Person Y and Person Z may not have been involved.

Test 5. Fingerprint Analysis Looking at the fingerprint analysis data in the table, who may have been involved in the death of Mr. Mathematics based on the right thumbprint found at the scene of the crime?

The fingerprint analysis suggests that Person X may have been involved in the mysterious murder of Mr. Mathematics and suggests that the other four boys may not have been involved.

Answers to Questions

1. As a result of the analysis for toxins, what was the likely cause of Mr. Mathematics’ death? Explain.

   Mr. Mathematics was likely poisoned by the fruit punch. His stomach contents were a light pink color and contained a poison. Poison was also found in the fruit punch and in the clear liquid contained in the beaker. Some of the clear liquid may have spilled into the fruit punch.

2. Based on the shoe size data from Coach Crunch, whose shoeprint may have been found at the scene of the crime? Explain.

   All of the boys, except Lenny Language, wore a size six shoe, the same size that was on the sheet of paper at the crime scene.

3. Based on the fiber analysis, whose clothing fibers may have been found at the scene of the crime? Explain.

   The fiber analysis showed that Lenny Language and Stanley Student were probably not at the scene of the crime since they wore nylon suits; however, the other three may have been there since they all wore cotton and cotton was found at the crime scene.

4. In the blood analysis, each suspect was assigned a letter for their blood sample. Use the key below to match the sample’s letter with the suspect. Whose blood may have been found at the scene of the crime? Explain.
   {12501_Answers_Table_10}

   The blood found at the crime scene was type O blood. Based on the chart, Henry History and Martin Mascot were the only two with type O blood. Lenny Language has type A blood, Bobby Booksmart has type B blood, and Stanley Student has type AB blood. Therefore, either Henry History or Martin Mascot may have been involved in the mysterious murder of Mr. Mathematics.

5. In the fingerprint analysis, each suspect was assigned a letter. They are the same letters used for the blood analysis. Whose fingerprints were found at the scene of the crime? Explain.

   The only fingerprint that matched the right thumbprint found at the scene of the crime was Henry History. The other fingerprints did not have the same distinctive whorl pattern.

6. Is there any one test that could have been performed to determine the identity of the suspect? Were any of the other tests unnecessary? Explain.

   Student’s answers will vary. Accept all reasonable answers. It appears that the fingerprint analysis may have been enough to determine, conclusively, the identity of the suspect.

Discussion

The crime scene investigators questioned Henry History and found out that the boys had been playing baseball when Henry hit the ball so hard that it broke the window in the teachers’ lounge. The ball hit the refrigerator, creating a dent, and knocked over some toner in the workroom. Henry climbed through the window, tearing his clothes and cutting his leg. When he stepped down from the window, he stepped into the toner. He then stepped on a sheet of paper, leaving a shoeprint, and reached down to pick up the ball. A few drops of blood dripped on the floor. He climbed back up on the windowsill, leaving a fingerprint, and then left the school to bandage his leg. The crime scene investigators conclude that the ball hitting the refrigerator must have caused the contents of the beaker to splash into the fruit punch, which was later consumed by Mr. Mathematics. As unfortunate as it is that Mr. Mathematics died, there will be no arrests today as it appears that his death was accidental.

Teacher Handouts

12501_Teacher1.pdf

Introduction

Using crime scene investigation techniques, solve the mysterious murder of Mr. Mathematics, the Mammals Middle School math teacher.

Concepts

• Forensic science
• Blood typing
• Evidence examination
• Fingerprinting

Background

Matthew Mathematics, the math teacher at Mammals Middle School, was mysteriously murdered on Monday morning. When Craig Crud, the campus custodian, came to clean the classroom before classes began that morning, he noticed the corpse of Mr. Mathematics and called the cops. The crime scene investigation team was sent to the school.

Upon entering the school, the crime scene team was escorted to the math classroom. They noticed the body of Mr. Mathematics on the floor. They did not find any suspicious items and observed that Mr. Mathematics’ body was free of any visible trauma (e.g., cuts, bruises or signs of struggle).

After assessing the math classroom, the crime scene investigations team began asking questions about the events that occurred before Mr. Mathematics died. The crime scene investigation team questioned all the teachers and staff in the building and discovered some very interesting facts. According to Priscilla Paper, the school secretary, Mr. Mathematics was in the teachers’ lounge earlier that morning to pour himself a glass of “something red” from a pitcher in the refrigerator. She saw him leave the lounge with the glass, to return to his classroom.

When the crime scene investigations team entered the teachers’ lounge they noticed that the window was broken and they also found a few fibers and some blood on the broken glass. They noted that the glass had been broken from the outside because the majority of it was on the floor inside the room. They collected the fibers and blood to analyze in the lab. A right thumb print was lifted from the windowsill. The investigators also noted a few drops of blood on the floor beside the refrigerator, a dent in the side of the refrigerator, and a shoe print on a piece of paper on the floor. Someone had stepped in some toner that was knocked over and then onto a sheet of copy paper that was on the floor. The shoe print was collected to analyze in the lab.

The crime scene investigators also examined the refrigerator. The refrigerator contained a pitcher of fruit punch, an opened bottle of catsup, a fruit smoothie and a beaker containing a clear liquid on the top shelf. All of these items were taken to the lab. There were no other suspicious items found in the teachers’ lounge. The team went to interview the principal before they returned to the lab to continue their investigation.

In talking to the principal, the crime scene investigators found that Nancy Neighbor, who lives across the street from the school, had called the principal, Pat Principle, and asked why all the police were at the school. She told Principal Principle that she saw five boys walking around the school track earlier that morning. The school athletics director, Coach Crunch, confirmed that he had also seen the boys walking around the track and playing baseball. No one else had been around the building that morning. Coach Crunch knew the boys and remembered their names. He had even issued socks to them with their athletic uniforms so he had their shoe sizes with the order. The crime scene investigation team asked Coach Crunch to identify the boys with as much detail as possible. The coach gave the investigators the following information about what the boys were wearing and their shoe sizes:

All of the boys were wearing gym shoes.

With this evidence, the crime scene investigators returned to the laboratory to determine the cause of death and the identity of the most likely boy involved in the murder. The size of the shoe, identity of the fibers, blood-type and fingerprints of the five suspects will be taken and the items from the refrigerator and stomach contents of Mr. Mathematics will be tested.

Experiment Overview

Perform crime scene investigation tests to determine which boy may have been involved in the mysterious murder of Mr. Mathematics.

Materials

Prelab Questions

1. Even though the teachers’ lounge is off limits to students, use your imagination to draw a sketch of what it might look like, including the location of the evidence found.
2. What should the custodian have done to preserve the crime scene before the authorities arrived that morning?
3. What might have happened to Mr. Mathematics and what evidence is involved?
4. What tests could be conducted to determine the person involved in the crime?
5. Before any tests are conducted, is there any conclusive evidence pointing to the people involved or the possible course of events?

Safety Precautions

Work carefully around candle flames. The “poison” in this lab is a dilute base, sodium hydroxide, which is corrosive to skin and eyes and moderately toxic by ingestion or inhalation. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

Part 1. Test for Poison

Determine how Mr. Mathematics died by testing the contents of his stomach for poison. If a poison is found, determine if he ingested it from one of the substances from the refrigerator.

1. Label each slide with the appropriate name of the red liquid.
2. Using a pipet, place four or five drops of each liquid from the refrigerator and the stomach contents sample onto a separate microscope slide.
3. Using the poison test strips provided by the teacher, dip a red test strip into the stomach contents of Mr. Mathematics.
4. Record the results of the test on the Mysterious Murder Worksheet. Note: Poison is present if the red test strip turns blue when dipped into the stomach contents.
5. If the stomach contents are positive for poison, test one of the other substances found in the refrigerator by dipping a fresh test strip into the liquid to see if it is positive for poison.
6. Record the results of each test strip on the Mysterious Murder Worksheet.
7. Repeat steps five and six for the other two substances.
8. Clean the microscope slides and put them aside for use in fiber analysis.

Test 2. Shoe Print

1. Use a metric ruler to measure the length in millimeters of the shoeprint on the Shoeprint Evidence Sheet.
2. Record the measurement on the Mysterious Murder Worksheet.
3. Compare the length of the shoe with the Comparative Shoe Size Chart found on the Mysterious Murder Worksheet to determine the shoe size of the person who made the print.
4. Record the shoe size on the Mysterious Murder Worksheet.

Test 3. Fiber Analysis

1. Observe the color, texture, appearance, etc. of the two types of known fabric samples, cotton and nylon with the naked eye.
2. Record all observations on the Mysterious Murder Worksheet.
3. Use forceps to place one of the cotton fibers on a microscope slide.
4. Add a drop of water to the slide, directly onto the fiber sample.
5. Cover the fiber with a cover slip.
6. Examine the fiber under the microscope at both low and high magnification.
7. Sketch the magnified view of the fiber on the Mysterious Murder Worksheet.
8. Repeat steps 3–7 with the nylon sample.
9. Observe the unknown fiber sample that was collected at the crime scene and record observations of the Mysterious Murder Worksheet.
10. Use forceps to place the crime scene fiber on a microscope slide.
11. Add a drop of water to the slide, directly onto the fiber sample.
12. Cover the fiber with a cover slip.
13. Examine the unknown fiber under the microscope at both low and high magnification.
14. Sketch the magnified view of the crime scene fiber on the Mysterious Murder Worksheet.
15. Carefully light the tea light candle.
16. Using forceps, hold one of the cotton fibers close to the flame.
17. Record any observations on the Mysterious Murder Worksheet. Note: Observations could include sounds, sights and smells.
18. Repeat steps 16 and 17 using first the nylon fiber and then the crime scene fiber.
19. Clean the microscope slides and put them aside for use in blood typing.

Test 4. Blood Analysis

1. Label six microscope slides—“V,” “W,” “X,” “Y,” “Z” and “CS.” Note: To conceal the identity of the person whose blood is being processed, each person has been given a letter for identification purposes. The identity of each person will be revealed after the tests are completed.
2. Place two or three drops of Person “V” blood on each end of the slide marked “V.” Similarly, place two or three drops of “W” blood on slide “W,” “X” blood on slide “X,” “Y” blood on slide “Y,” “Z” blood on slide “Z” and “Crime Scene” blood on the slide labeled “CS.” Use a clean pipet with each sample.
3. Using a clean pipet, add two drops of Anti-A Sera to the blood on the left side of each slide. Similarly, add two drops of Anti-B Sera to the right side of each slide.
4. Stir the mixtures in all 12 locations. (Use a different clean toothpick for each sample. Use only one toothpick per spot to avoid cross contamination.) Mix each sample thoroughly and let the slides set for at least two minutes.
5. Observe each spot against a white background (paper) and record the results on the Crime Scene Worksheet. Note: If the blood clumps, place an “X” under the appropriate Anti Sera (A or B). The serum that clumps the blood indicates the blood type. If both clump the blood is type AB and if neither clumps the blood is type O blood.
6. Dispose of all materials as directed by your instructor.

Test 5. Fingerprint Analysis

1. Observe the Fingerprint Evidence Card. Note: The fingerprint card contains prints of the five suspects (labeled “V,” “W,” “X,” “Y” and “Z”) and the one lifted at the crime scene (labeled “CS”). The same letters that were used for each suspect were also assigned to the fingerprint samples to conceal the identity of the suspects until all tests are completed.
2. Use the information of the Fingerprint Background Information Sheet to determine if there is a match between the fingerprint found at the crime scene and that of one of the suspects.
3. Record the results of the fingerprint analysis on the Crime Scene Worksheet. Explain why the fingerprints match and who needs to be questioned further in the mysterious murder of Mr. Mathematics.
4. Consult your instructor for appropriate disposal procedures.

Student Worksheet PDF

12501_Student1.pdf