This chapter presents the subject, explains its use, and provides examples of how some of the probability estimates are derived by intelligence and criminal analysts. It also provides some of the math concepts involved, how and why probability is used in analysis, show examples of its more recent impact on criminal and intelligence, and provide a few tools to help make analytical probability estimates. In probability theory, the normal distribution is a very common probability distribution. Theoretical probability is calculated probability. The concept of conditional probability is one of the most basic, fundamental, and at the same time one of the most important concepts in probability theory. The chapter looks at areas where probability plays significant roles in the solving of crimes and driving law enforcement and criminal justice policy. Probability and statistics not only can be used to identify suspects, support investigations, and obtain convictions, they can also be used to deter criminal behavior.