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The popularity of such shows as CSI or Bones has increased interest in forensic science and its applications for may students. The following program is a series of experiments that will teach students about fingerprinting, chemical analysis and blood spatter. The resulting skills can be used to solve a crime and determine the guilty suspect.
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Everyone has a unique fingerprint. This activity will teach students how to take fingerprints and compare them to existing samples to get a match. Once the students have practiced this skill they can move on to the second skill required in this forensic program.
The simplest means of getting a fingerprint is to rub a pencil on a piece of paper to create a square as large as the finger. Rub your finger across the graphite of the pencil and then roll it across the sticky side of a piece of tape. Place the tape sticky side down on a piece of white cardstock. This creates a fingerprint that can be compared to existing prints. Have the students practice in pairs. Write the person’s name on the back of each fingerprint and set it aside for use later. Switch pairs and have the new groups take fingerprints and then try to match them correctly to the previously taken samples. Once this skill is mastered the students can move on to the next experiment.
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Chemical Analysis Activity
In television shows there is frequently a department or expert who works with physical evidence located at the crime scene. Sometimes this evidence is an unidentified powder. In this experiment the students will practice observing and testing the characteristics of a white powder to determine what it is. This experiment will use sugar, baking soda, baking powder, cornstarch, flour and baby powder.
Give each student a small amount of each powder. Caution them that taste is NOT one of the ways to test a substance, as it may be poisonous. Instruct students to test each substance for texture first. Then test for a reaction to vinegar, water, and iodine. The baking soda and baking powder will react to the vinegar with bubbles. However they will turn different colors with the iodine. The sugar can be identified by texture. The baby powder will react with the water and iodine, but not the vinegar. The cornstarch will float on the water and react to both vinegar and iodine. Once the students have completed the experiment and gathered their data they can verify their findings. If someone has an incorrect finding have them review the steps followed to ensure they understand proper procedures for testing. After completing the testing process correctly the students are ready to move onto the final method of forensic detection.
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Blood Spatter Activity
Murder mysteries often make use of the pattern of blood as it appears after the crime has been committed. This pattern can be used to determine the location of the attacker in relation to the victim and the location of other objects around the victim. Students will use water balloons to study the patterns created by a liquid.
Divide students into pairs and give each at least nine water balloons. Each experiment is done three times for comparison and should be done outside. The first trial requires the students to drop the water balloon onto a cement surface from a height of 5 feet. The second phase is to throw a water balloon at a wall from a distance of 6 feet. The final phase of the experiment is to drop the water balloon on a step and observe the result. Each test should be repeated with an object such as a knife or corkscrew in the drop area to illustrate the pattern when an object is present and then removed. The distance from the ground and from the wall can be varied for additional trials if desired. Take pictures of each scenario to be used as part of the final mystery.
Now that the students have mastered these three aspects of forensic detection a mystery can be presented for them to solve.
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Prepare for the mystery portion by randomly choosing one of the fingerprints taken by students in the first activity. This fingerprint will be that of the unidentified attacker. Tell the students the following story:
There once was a wealthy man who was having an open house party for his oldest daughter to celebrate her graduation. The party included a buffet, cake, bar and dancing. There were a lot of guests coming and going throughout the party and a nanny had been hired to care for the guests’ young children. After the party one of the people cleaning up found blood spatter and evidence of a struggle on the patio. The police were summoned and subsequently found several different fingerprints and an unidentified white powder on an overturned tabletop. A broken clock nearby pinpoints the time of the attack as 4:00 p.m., which narrows the number of suspects to four: The bartender, the baker, the nanny and the caterer. Students must identify the attacker.
The students will need to take fingerprints from each other and compare them to the designated ‘victim’ fingerprint and the ‘attacker’ fingerprint to determine which is which. Students can use the same process as previously used to identify the white powder substance. The white substance will identify the attacker. For the baker it should be baking soda, for the nanny, provide baby powder. The bartender would leave salt and the caterer would leave cornstarch. Provide a photo of blood spatter with a void area in the shape of an object frequently used by the attacker. The baker would use a knife for cutting cakes and the nanny may have a steak knife from the buffet. The bartender would have a corkscrew, and the caterer would have a large knife for cutting meat. Allow the students to study the clues and determine who is the attacker.