Have children use an ink pad to take their fingerprints and put them on a piece of paper out of sight of the other children. Through analyzing the different prints, they can figure out whose prints belong to whom. Another idea is to have one of the children press an oily or sticky finger on the side of a glass and then dust the print with cocoa powder. Brushing with a camelhair or fiberglass brush will let the fingerprints remain so that the child can use a piece of tape to lift the fingerprint off the glass and press it onto a piece of paper.
Teach children about the importance of proper evidence handling. Set up a small crime scene with mock items such as a pretend knife, gun or pieces of paper to act as broken shards of glass. Have them read guidelines and evidence handling procedures from a particular state, such as Montana, New Jersey or North Carolina. Watch as they collect the evidence, and make sure they maintain the guidelines of the state they selected.
Have one child write a cryptic note that relates to a particular crime scene, such as a ransom note. Awhile later, have all of the children go into separate rooms and write their names or a brief sentence on a piece of paper. Bring the group back together to conduct handwriting analysis with rulers, protractors and microscopes to analyze and measure the samples to determine who wrote the ransom note.
Cover the floor of the room with a large sheet of paper. Set up a crime scene such as a murder or a break-in through a glass window. Make different types of blood splatter markings on the sheet of paper. Have the students or children determine factors such as which direction the blood came from, how the shape of the blood shows where the blood hit or if the blood was a result of a gun by analyzing the blood patterns.