Because the majority of the clues are footprints, it is very important for the field teams to have information on the length, width, and, if possible, sole pattern of the subject's footgear. This will allow the teams to concentrate on a subset of the total number of prints that they encounter. Clue detection involves both knowing how to look for clues and how to interpret what is seen. Clues are disturbances to the natural environment caused by the subject passing through the area. Detection of clues requires the use of visual skills of the observer.
Light is used to make the clues observable.
To maximize the observer's visual acuity, it is important to optimize the lighting conditions based upon the available resources. It is generally easiest to detect clues by visually scanning the ground while facing the light and with the light source at a low angle to the ground. This often means that a tracking team member moves around to face the light source, but it must be done carefully, so that, clues are not destroyed. It is also sometimes helpful to turn around and look back while tracking, to view a different perspective of the scene. At night, an observer can control the light angle.