Forensic scientists, lawyers and other participants of the legal process are routinely faced with problems of making decisions under circumstances of uncertainty. Uncertainty relates to propositions of interest that are not completely known by the decision-maker at the time when a decision needs to be made. Around the middle of the past century, discussions intensified and several fields of study emerged on decision-making concerning, for example, contexts where decisions have monetary consequences. Decision theory is a mathematical theory of how to make decisions when there is uncertainty about the true state of nature. The presence of uncertainty implies that a choice among the alternative courses of action leads to uncertainty regarding which consequences will effectively take place. The principal issue in decision making under uncertainty is the selection of a member in the list of available decisions without knowing which state of nature is truly the case.