The sample taken from a crime scene is matched with a location at a crime scene based on the ratio of diatom species present. Because diatoms can also be in the air and transferred to people through contact, breathing, eating, and drinking forensic scientists want to establish a base line or percent of error. Samples are taken off of clothing and objects of suspects and around the area of the crime scene and then tested to see the ratio of diatom colonies present before the alleged incident occurred.