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Set Up Procedures: Crime Lab

Kathy Paris

The students' job is to study the evidence given to them and try to figure out the name of the guilty party. For example, a student team would be given tray "N" with the evidence gathered at the scene. Tray "N" contained a vial of flour, one of glucose, an envelope with scales in it, a slide with blood on it, a margarine container with small pebbles and a set of fingerprints. On the students' procedure sheet (Crime Lab Activity) it gives this information:

        Crime Suspect List

  1. Todd is a baker at the local Safeway store. He often samples his creations, but prefers candy and other sugary items. He lives in a inexpensive apartment near the South Hill Mall. He has a pet that hisses. He often cuts his hands either on the job or when he cleans pebbles in his pet's tank.

As you see from the evidence items listed below in Tray N, the clues point to Todd. Tray B also contains the same evidence and points to Todd. I make sure that the evidence trays are widely distributed in the class so two lab teams next to each other do not have the same suspect.

I obtained 15 small trays and labeled them A-O. These trays would hold the evidence gathered at the scene. Since I wanted to save effort on my part, several trays were set up with the same evidence. I used small glass tubes, empty margarine containers, plastic bags and envelopes to put the evidence.



Suspect and Clues (the items in bold type are to go into the evidence tray; the words not in bold type are clues for you only)

Suspect 1 (Todd): flour-baker; glucose (should actually be sucrose but I couldn't find a test for disaccharides)-diet; scales-snake; pebbles-pet; blood slide-cut himself (Trays N and B).

Suspect 2 (Eileen): rocks-geologist: dog hair-pet; starch-diet; oil-chips; slide with red dye-paint; (Trays O and J).

Suspect 3 (Mary): scales-snake; blood slide-bites her; protein-diet; pieces of plants-botanist; glucose-diet; talcum powder-she uses. (Tray I)

Suspect 4 (Shelley): sand-job; slide with red dye-job; scales-snake; starch and glucose-diet; powder-for snake. (Tray C)

Suspect 5 (Rob): oil-diet; slide with red dye-painter; fish scales-fish pet; starch-diet; slide with blood-cut himself. (Trays K and D).

Suspect 6 (Nancy): eraser rubbings-job; cat hair-pet; slide with blood-cat bites; protein and oil-food for cat. (Tray A)

Suspect 7 (Bob): dirt-grave digger; cat hair-pet; starch-diet; protein and oil-lunch; powder-for hands; slide with blood-hands hurt. (Tray M)

Suspect 8 (Don): dirt-job; scales-fish pet; glucose-for pet; slide with blood-cuts; powder-for hands; protein, starch and oil-lunch (Tray G and H)

Suspect 9 (Verne): sand-job; dog hair-pet; slide with red dye-paint; starch and protein-pet food (Tray L and F)

Suspect 10 (Sam): dirt-job; rock-pet; glucose and starch-diet; slide with red dye-paint; pieces of plants-job (Tray E)



HINTS:


  1. I used albumen for the protein, glucose for the sugar and soluble starch. The first time I did this lab, I put all the samples in separate small containers. This made it too easy on the kids--once they found that a sample was such and such, they didn't do the other tests on that sample. The next time I will mix all the dry sample into one container, This will force the kids to do all the tests. The oil still needs to be put into separate containers, but I throw a sample of water into all the trays so they are forced to do the fat test. The water sample is in the exact same size/shape container as the oil (if oil is to be a clue).

  2. The lab takes about 2 days.

  3. Expand your list of clues/descriptions to make the lab more difficult.

  4. Pictures of suspects can be obtained from magazines; just make sure you select an ethnic diversity and include both males and females and different ages.

  5. Fingerprints:

    1. Do not show to students until suspects are narrowed to two.

    2. It's a good idea, but not essential, to have done a fingerprint lab earlier.

    3. To make fingerprints, all you will need is some scratch paper, pencils and clear tape. Have students make about a 1-2 inch square with their pencil on the scratch paper. It should be very dark with lots of graphite. They then thoroughly rub one finger in the graphite square. A piece of 3/4th tape is applied to that finger and pressed on firmly. The tape is then removed and applied to another piece of scratch paper onto which the hand has been traced. They tape the imprint of each finger over the appropriate finger on the tracing.

    4. You'll need 10 sets of fingerprints--I asked one of my classes to make two copies of the same hand; I selected the 10 best sets and put one copy in the clue tray given to the students and one copy on the back of the picture of each of the suspects.

  6. You'll need 20 envelopes for hair samples (kids love to donate to the "cause"); two envelopes for one type of hair sample; one envelope goes in clue tray, one goes with the picture and is only given to the students when suspects are narrowed down to two. Important: make sure that the color of the hair matches the picture of the appropriate suspect.

  7. Demo results of a positive starch, sugar (glucose) and protein test.



Activity     Evidence Sheet     Answer Key




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