Crime scenes display two types of fingerprints: visual, which can be seen by the eye, and latent, which are not visible. Latent prints can be seen through many different processes, such as fuming with glue or using fingerprint powder. Create an experiment in which children test different materials to dust for fingerprints using different techniques. Items that can be used include chalk, graphite, charcoal and iron filings with magnets. Different dusting techniques include using brushes to lightly apply the powder, adding a large amount of powder to an area and shaking off the excess powder to find prints and running magnets with iron filings. Have the students determine which powder and technique provides the best print.
Crime scenes are not only about the physical evidence present at the scene. Witnesses play a large role in aiding authorities in finding suspects. Test how good a witness' testimony and memory is. Cut out different facial features from magazines, such as eyes, noses, mouths and hair styles. Create a composite of an individual and show it to other students. Place the composite features into a basket with many other features. Ask the students to recreate the face shown to them 10 minutes later. How well did the witnesses do at recreating the face?
Chromatography is a process to identify pigments. This experiment will determine if the suspect used the same pen as he did at the crime scene. Provide the students with felt pens and have them place a dot of ink on a strip of paper towel. Place the paper towel into a dish of water below the dot. The water will "climb" up the towel and will separate the pigments in the pen as the water rises. If the pens are the same, they will display the same pigment features.
Have students work on their observational skills when identifying mystery powders. Some powders that can be used are sugar, salt, cornstarch, chalk and baking soda. Place the powders in different areas around the room. Allow the students to examine the powder through a magnifying glass and use their sense of touch and smell. Do not let them taste the powders unless all of the powders are edible. Simple tests can be performed, such as adding water or vinegar to the powder in paper cups and writing down the results. The students must make their best guess as to which powder they have been given. For children in early grades, provide information on different reactions, such as that by adding vinegar to baking soda will create large amounts of bubbles.
Elements burn different colors when exposed to heat. Crime scene analysts must sometimes find out what a material is made out of. This experiment works best for high school students. Use a Bunsen burner, a wire and different elements dissolved in solution. Elements for testing include sodium, potassium, barium, calcium, copper and lead. A student should dip the test wire into the solution and hold the wire over the flame. The student should then write down what color was observed in the burning process. Use new test wire for each solution to avoid contamination. Provide students with a chart showing what colors appear when elements are burned. The students should then match their observations to the chart.