In many actions at law or cases in equity the judge is not required by statute or precedent to make a predetermined decision; but is able to make a decision within a range of decisions. For example, in determining custody of children in cases of dissolution of marriage (divorce), after condsidering certain factors, which may be set out by statute, the judge may grant custody to the father, the mother, or both, upon the same facts, assuming both are capable parents. Ordinarly, an appellate court will grant deference to the discretion of the trial court and would not overturn any of those 3 decisions unless an error of Law occurred and/or there was a palpable error in the assessment of evidence.

A judge may abuse discretion. To continue our example, if one parent is very incapable and the other very capable (assuming this is shown by the evidence), if a judge grants custody to the poor parent; it may be possible on appeal to overturn the decision. Nevertheless winning such an appeal will be difficult as the presumption both in law and as a practical matter is that the trial court knew what it was doing as the trier of fact (often not the judge, but the jury in other types of cases not requiring the court to exercise equity) is in the best position to review the testimony and other evidence. Except in extraordinary cases, appellate courts only review the written record of lower court decisions.