Proximate cause (sometimes called legal cause) is the requirement that, even where a defendant's conduct is a factual cause of an injury, liability attaches only if the harm bears a close enough relationship to that conduct. It operates as a policy-driven filter on top of the "but-for" test of factual causation, preventing infinite chains of liability stretching from a single act.
In common-law tort systems, courts typically apply one of two main tests. The foreseeability test, dominant in most U.S. jurisdictions and articulated in Palsgraf v. Long Island Railroad Co. (N.Y. 1928), asks whether the type of harm and class of plaintiff were reasonably foreseeable from the defendant's negligence. The direct consequences test, associated with the English decision in Re Polemis (1921), focuses on whether the harm flowed directly from the act without intervening causes; it was largely displaced in Commonwealth jurisdictions by Overseas Tankship (UK) Ltd v Morts Dock & Engineering Co (Wagon Mound No. 1, Privy Council 1961), which adopted foreseeability.
Key concepts that operate within proximate-cause analysis include:
- Intervening cause: an event occurring after the defendant's act that contributes to the harm.
- Superseding cause: an intervening cause significant enough to break the chain of liability.
- Eggshell-skull rule: a defendant takes the plaintiff as found, so unforeseeable extent of harm does not defeat proximate cause if the type of harm was foreseeable.
Proximate cause appears beyond tort law. In criminal law, it limits homicide liability where intervening acts (e.g., grossly negligent medical treatment) sever causation. In international law and investor-state arbitration, tribunals invoke analogous remoteness principles when assessing damages — the International Law Commission's Articles on State Responsibility (2001), Article 31, references injuries "caused by" a wrongful act, and tribunals frequently exclude harms deemed too speculative or remote. In U.S. statutory contexts, the Supreme Court applied proximate-cause limits to civil RICO suits in Holmes v. Securities Investor Protection Corp. (1992) and to Lanham Act claims in Lexmark Int'l v. Static Control (2014).
Example
In *Palsgraf v. Long Island Railroad Co.* (1928), the New York Court of Appeals held that a railroad employee's push that dislodged a passenger's fireworks was not the proximate cause of injuries to Helen Palsgraf standing far down the platform, because harm to her was not reasonably foreseeable.
Frequently asked questions
Factual (but-for) cause asks whether the harm would have occurred absent the defendant's act; proximate cause asks whether the connection is close enough — in foreseeability or directness — to justify imposing liability.
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