Materials Included In Kit

Additional Materials Required

Prelab Preparation

1. Label each pen with the name of one of the suspects (Patty Pfluger, Danny Daschund, Sherri Showoff, Brandon Barker and Pat Poodle).
2. Write the following statement on one of the sheets of chromatography paper and affix it temporarily (so that it may be photocopied) to the Plaintown Pooch Parlor Comment Card. Note: The pen chosen to write this statement is the pen for Sherri Showoff who stole Priscilla.

   “Thank you so much for your hard work grooming Priscilla. Hopefully there will be some big news regarding her and the dog show in Dogville. I bet you will see a story about her in tomorrow’s paper.”

3. Using the same pen, write the following sentence on the Handwriting Analysis Sheet for Sherri Showoff.

   “The quick brown fox jumps over the lazy dog.”

4. Make enough copies of the Comment Card and the Handwriting Analysis Sheet for each lab group.

Safety Precautions

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 consult 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 materials in this lab may be disposed of according to Flinn Suggested Disposal Method #26a and #26b.

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 Post-Lab Questions may be completed the day after the lab.
• Switch pens for the ink analysis and explain to students after they finish their results that the criminal used another suspect’s pen so that the test would not have conclusively pointed to the correct individual.
• Toothpicks may be wiped clean and resused, if desired.

Sample Data

Test 1—Blood Analysis

Looking at the blood analysis data in the table, who may have been involved in the abduction of Priscilla, if anyone? Does it show that someone may not have been involved?

The blood analysis suggests that either Person V or Person X may have been involved in the abduction of Priscilla from the Plaintown Pooch Parlor. It suggests that Person W, Person Y and Person Z may not have been involved.

Test 2—Ink Analysis (Paper Chromatography)

Looking at the ink (chromatography) analysis data in the table, who may have been involved in abduction of Priscilla based on the pen (ink) used on the Plaintown Pooch Parlor Comment Card, if anyone?

Students’ answers will vary depending on whose pen was used to write the letter. Sherri Showoff took Priscilla in this scenario. If her pen where used, the ink analysis would suggest that she was involved in the abduction as well as any other suspect who used the same type of pen.

Test 3—Handwriting Analysis

Looking at the handwriting analysis data in the table above, who may have been involved in abduction of Priscilla based on the comment written on the Plaintown Pooch Parlor Comment Card, if anyone? Explain.

Answers will vary based on the suspect’s (teacher’s) writing characteristics. The handwriting on the Plaintown Pooch Parlor Comment Card closely matches the handwriting sample for Sherri Showoff, indicating that she may have been involved in the abduction of Priscilla.

Test 4—Fingerprint Analysis

Looking at the fingerprint analysis data in the table above, who may have been involved in the abduction of Priscilla based on the fingerprint found on the cup left at the Plaintown Pooch Parlor, if anyone?

The fingerprint analysis suggests that Person X may have been involved in abduction of Priscilla from the Plaintown Pooch Parlor and suggests that the other four suspects may not have been involved.

Answers to Questions

1. Was there enough evidence before the analyses were performed to eliminate any of the suspects?

   No.

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

   Sample Letter—Suspect
   V—Danny Daschund
   W—Patty Pfluger
   X—Sherri Showoff
   Y—Brandon Barker
   Z—Pat Poodle
   The blood found at the crime scene was type O blood. Based on the chart, Danny Daschund and Sherri Showoff were the only two with type O blood. Brandon Barker has type A blood, Pat Poodle has type B blood, and Pat Pfluger has type AB blood. Therefore, either Danny Daschund or Sherri Showoff may have been involved in taking Priscilla from the Plaintown Pooch Parlor.

3. 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 one found on the cup at the Plaintown Pooch Parlor was that for Sherri Showoff. The other fingerprints did not have the same distinctive whorl pattern.

4. 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.

   Students’ answers will vary. Accept all reasonable answers. It appears that the fingerprint analysis or handwriting analysis may have been enough to determine, conclusively, the identity of the suspect; however, the other evidence backs up the identity of the suspects to allow the crime scene investigators to remove doubt in positively identifying the suspect.

Teacher Handouts

12767_Teacher1.pdf

Introduction

Use science to discover the person who committed a criminal act. As a forensic scientist, you will use the information gathered in the “Detective’s Casebook” to determine the identity of the person who stole Bobby Bedhead’s prize-winning pooch Priscilla.

Concepts

• Chromatography

• Fingerprint analysis
• ABO blood typing
• Handwriting analysis

Background

The statement in the detective’s casebook reads as follows: Bobby Bedhead arrived at the Plaintown Pooch Parlor this afternoon to find that his prize-winning pooch Priscilla had already been picked up after her day at the groomers. Bobby was preparing her for the dog show in Dogville, tomorrow. When Bobby was questioned, it became clear that the only people who may have stooped so low as to steal Priscilla would have been Bobby’s dog show rivals, Patty Pfluger, Danny Daschund, Sherri Showoff, Brandon Barker or Pat Poodle.

The owner of the Plaintown Pooch Parlor, Mrs. Rottweiler, said that she had been very busy grooming dogs so her assistant handled the transactions when the clients paid for the grooming services. The assistant was not available for comment, but Mrs. Rottweiler remembers that she complained that “the person who came to pick up Mr. Bedhead’s dog left a cup on the counter.” A print from the cup was retrieved and taken back to the lab to be analyzed. Mrs. Rottweiler also stated that “we need to buy more pens because every customer has had to use her own pen to sign the log book.” A pen was not found at the counter.

All owners must sign their dogs in and out in the log book. The entry in the daily log book revealed that the dog bit the person who picked her up. A few drops of blood were observed on the side of the cash register and collected for blood typing.

The culprit left a note on a comment card. The comment reads as follows: “Thank you so much for your hard work grooming Priscilla. Hopefully there will be some big news regarding her and the dog show in Dogville. I bet you will see a story about her in tomorrow’s paper.” The card was collected to analyze the ink and handwriting.

All five suspects in the case were called in to provide fingerprints, blood samples and writing samples, and the ink pens in their pockets and purses were confiscated for comparison against the evidence collected at the crime scene.

Experiment Overview

You are a forensic scientist who must solve the mystery of who stole Priscilla from the dog groomers. Find the culprit using paper chromatography, fingerprint analysis, handwriting analysis and blood typing. Identifying the correct suspect will allow Priscilla to be returned to her owner in time for the dog show in Dogville.

Materials

Safety Precautions

Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

Test 1—Blood Analysis (ABO Blood Typing)

1. Label six microscope slides: “V,” “W,” “X,” “Y,” “Z” and “CS.” Place the slides on a sheet of white paper. 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. The blood collected from the Plaintown Pooch Parlor is labeled “CS” for “crime scene.”
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 each end of 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.”
3. Carefully add two drops of Anti-A serum to the blood on the left side of each slide. Similarly, add two drops of Anti-B serum to the right side of each slide.
4. Using a toothpick, stir the mixture in each location on the slides. Use a different clean toothpick for each location. Use only one toothpick per spot to avoid cross contamination. Mix each thoroughly and let the slides sit for at least two minutes.
5. Observe each spot against a white background (paper) and record the results on the Detective’s Casebook Worksheet. Note: If the blood clumps, place an “X” under the appropriate Anti Sera. The serum that clumps the blood indicates the blood type. If both Anti serum A and B clump, the type is AB and if neither clumps the blood type is O.
6. Dispose of all materials as directed by your instructor.

Test 2—Ink Analysis (Paper Chromatography)

1. Obtain a beaker or plastic cup.
2. Place enough distilled water in the container so that the water is about 1 cm deep.
3. Obtain a piece of chromatography paper (20 cm square) and cut a 1 cm wide strip from one edge. This cut edge is now the top of the paper.
4. Using scissors cut a 1 x 1 cm square of writing from the Comment Card. Note: A copy of this card has already been made for handwriting analysis later in the lab.
5. Using a stapler, staple the square of writing to the piece of chromatography paper with the ink touching the chromatography paper. The square should be stapled at least 2 cm from the side of the chromatography paper and 1 cm from the bottom edge (see Figure 1).
   {12767_Procedure_Figure_1}
6. Cut five 1-cm squares from the 1-cm strip of chromatography paper that was cut off in step 3.
7. Using the pens confiscated from the suspects, make a mark with each pen on a separate 1-cm chromatography paper squares. Space the squares at least 2-cm apart.
8. Using a stapler, staple each square to the large piece of chromatography paper in same manner as the one from the Comment Card. The ink should be facing the large piece of chromatography paper.
9. Using a pencil, write the name of each suspect at the top of the chromatography paper above the corresponding ink sample and the piece cut from the Comment Card.
10. Fold the chromatography paper into a cylinder so that the stapled squares are on the outside. The sides should overlap by about 1 cm.
11. Using a stapler, staple the sides together close to the top and bottom of the chromatography paper cylinder as shown in Figure 2.
    {12767_Procedure_Figure_2}
12. Place the chromatography paper cylinder in the cup or beaker and allow the water to travel to within 1 cm of the top of the chromatography paper.
13. Compare the components of each ink sample and identify a match with the ink used to write the comment on the Comment Card.
14. Record the ink analysis observations on the Detective’s Casebook Worksheet.

Test 3—Handwriting analysis

1. Examine the five handwriting samples on the Handwriting Analysis Sheet and identify variations in each suspect’s writing characteristics.
2. Compare the writing sample on the copy of the Comment Card with those collected on the Handwriting Analysis Sheet.
3. Determine any significant matches in the way the letters are formed by pen movements and in the fine detail of each letter. Note: Compare lower-case letters to lower-case letters and capitals to capitals of the same letters only. Look for significant matches or mismatches in letter formation, fine detail of the letters, proportion and size of letters, parts of compound letters, such as “g” and “k,” ornamentation and flourishes in letters, slant, links or spaces between letters, and quality of the ink.
4. Identify the closest match between the writing on the Comment Card and writing sample supplied by the suspects on the Handwriting Analysis Sheet.
5. Record the name of the suspect whose handwriting most closely matches that on the Comment Card and give as many examples as possible for the positive identification on the Detective’s Casebook Worksheet.

Test 4—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”) as well as the fingerprint lifted from the cup left at the Plaintown Pooch Parlor (labeled “CS”). Note: The same letters that were used in the blood analysis 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. Note: There should be at least ten points of commonality.
3. Record the results of the fingerprint analysis on the Detective’s Casebook Worksheet. Explain why the fingerprints match and who needs to be questioned regarding the disappearance of Priscilla.
4. Consult your instructor for appropriate disposal procedures.

Student Worksheet PDF

12767_Student1.pdf