But-For Test Law and Legal Definition

But-For test is a doctrine which states that causation exists only when the result would not have occurred without the accused party’s conduct. This is shorthand for whether the action was the "proximate cause" of the damage. The "but for" test is the standard that must be met in order to prove causation in attorney disciplinary cases involving alcoholism. [In re Kersey, 520 A.2d 321 (D.C. 1987)].

This test used in tort and criminal law to determine a defendant's responsibility for the subject of a lawsuit or criminal proceeding. In Criminal law, it is also termed as had-not test.