Sometimes judges, in their opinions, say things that are not strictly necessary to support their decisions. Because our legal system depends heavily on the reasoning contained in prior decisions (the principle known as stare decisis) loose words contained in a judicial opinion can cause problems for later cases.
For example, a judge in an automobile accident case, who finds one of the drivers responsible for driving through a red light, might also say in his opinion that although the accident was caused by the red light violation, the intersection is notoriously bad anyway. In a later case involving the same intersection, a driver injured in a different accident might seek to hold the government responsible because it is a bad intersection, citing the earlier case.
The judge’s comment about the intersection being dangerous was not necessary to his decision finding the driver responsible because of the red light violation. The comment about the intersection is known as obiter dictum.
Obiter dictum is a statement in a court opinion where judges make observations that have no actual bearing on the decision of the issue at hand. Later courts generally disregard such statements and do not give them precedential value. Judicial opinions should be confined to the precise facts and circumstances of the case being decided and judges should not indulge in generalities or off the cuff remarks which might have an unintended effect on future decisions.
— Kevin Palmer