The most important evidence rules for surveyors concern expert witnesses. When a surveyor gives a court his or her opinion as to the “correct” way to survey a property, he or she is playing the role of expert witness. Experts have a wider latitude in testifying than “lay” or “eye” witnesses, and this can be beneficial when you are justifying the use of a particular monument or method that another surveyor opposes. The most notable advantage of being declared an expert is that you can base your opinion on evidence that is otherwise inadmissable, which usually boils down to using hearsay.
Evidence rules compile a long common law history of rulings from reported cases into a concise, easy-to-follow form. Various institutions write compilations of different aspects of the common law, for example the “restatements” of such areas as property law or torts, some of which require volumes in their own right. The rules of evidence were originally a similar attempt to compile the common law on the presentation of evidence in federal courts. Many states followed the example, often copying the federal rules with few, if any, changes. Unlike the restatements, which are treatises and may or may not be adopted by the courts on a case-by-case basis, the evidence rules, in the federal courts and in many state courts, have been codified as a group.