Synopsis: This unit looks at the visible and infrared sections of the electromagnetic spectrum and their use in detecting latent evidence at crime scenes and testing it in the lab. Visible light is used in a type of spectroscopy which can identify an unknown substance and determine its concentration. Infrared light can be used to visualize hard to see evidence like blood and gunshot residue on dark colored clothing. Further, that evidence can be photographed with an IR sensitive camera and preserved for later investigative use. After discussing the science of light, this curriculum unit introduces the reader to several labs that can be done in the high school classroom to reinforce these concepts.