ABSTRACT
The fourth step in legal reasoning is to research the facts to which the law must be applied. The law has its own unique rules for factual investigation. To a scientist, a fact is that which can be empirically observed. To a lawyer in a dispute, a fact is that which can be proved to a jury or to a judge sitting as the finder of fact. The law of evidence prescribes rules that govern factual investigation in a court of law. In general, the jury is permitted to consider two types of evidence: oral testimony and physical objects, such as a document, a photograph, or a knife. Evidence is admissible only if it is relevant, that is, it tends to prove or disprove a fact of consequence to the action. The psychological literature has documented a variety of cognitive biases that affect judges and juries. Cognitive biases are often in the form of heuristics.
