An act from which an injury results as a natural, direct, uninterrupted consequence and without which the injury would not have occurred.
Proximate cause is the primary cause of an injury. It is not necessarily the closest cause in time or space nor the first event that sets in motion a sequence of events leading to an injury. Proximate cause produces particular, foreseeable consequences without the intervention of any independent or unforeseeable cause. It is also known as legal cause.
To help determine the proximate cause of an injury in negligence or other tort cases, courts have devised the "but for" or "sine qua non" rule, which considers whether the injury would not have occurred but for the defendant's negligent act. A finding that an injury would not have occurred but for a defendant's act establishes that the particular act or omission is the proximate cause of the harm, but it does not necessarily establish liability since a variety of other factors can come into play in tort actions.
Some jurisdictions apply the "substantial factor" formula to determine proximate cause. This rule considers whether the defendant's conduct was a substantial factor in producing the harm. If the act was a substantial factor in bringing about the damage, then the defendant will be held liable unless she can raise a sufficient defense to rebut the claims.