Negligence: Cause in Fact

The Causation Framework

Negligence causation has two components: 1. Cause in fact (actual cause) — Did defendant's breach actually cause the harm? (This week) 2. Proximate cause (legal cause) — Is the harm within the scope of liability? (Next torts week)

Both must be proven. Cause in fact is the factual question; proximate cause is the policy question.

The But-For Test

The Standard Test

But for the defendant's negligent conduct, would the plaintiff's harm have occurred?

- If NO (harm would NOT have occurred) → Cause in fact established - If YES (harm would have occurred anyway) → No cause in fact; claim fails

Application

| Scenario | But-For Satisfied? | |----------|-------------------| | D runs red light, hits P | Yes — but for running the light, D would have stopped and P would be unhurt | | D prescribes wrong medication, P gets sicker | Yes — but for wrong medication, P would have received correct treatment | | D fails to install smoke detector, fire kills P who was already unconscious from smoke | Maybe — would the alarm have saved P? Factual question | | D is one of two drivers who simultaneously run P over | But-for FAILS — see substantial factor below |

When But-For Fails: Concurrent Causes

The Problem

Two independent fires merge and burn down plaintiff's house. Each fire alone would have destroyed the house. Under but-for: 'But for Fire A, would the house have burned? Yes — Fire B would have destroyed it anyway.' The same logic applies to Fire B. Result: neither defendant is the cause in fact, and plaintiff recovers from no one. This is unjust.

The Substantial Factor Solution

When two independent causes are each sufficient to produce the harm, courts apply the substantial factor test: Was defendant's conduct a substantial factor in bringing about the harm?

Each defendant is liable because each contributed substantially — even though but-for analysis would excuse both.

Alternative Liability: Summers v. Tice

The Problem

Two hunters shoot simultaneously at the same bird. One pellet hits plaintiff. Plaintiff cannot prove which hunter fired the injuring shot.

The Solution

Burden shifts to defendants. Each defendant must prove they were NOT the cause. If neither can carry that burden, both are liable.

Requirements

1. All defendants acted negligently 2. Plaintiff was harmed by one defendant's negligence 3. Plaintiff cannot determine which defendant caused the harm through no fault of plaintiff's own

Market Share Liability

The Problem (Sindell v. Abbott Labs)

Thousands of women were harmed by DES (a drug). Many manufacturers made identical DES. Decades later, plaintiffs cannot identify which manufacturer supplied their mother's pills.

The Solution

Each manufacturer is liable in proportion to its market share — if a company had 20% of the DES market, it pays 20% of the damages.

Strict Requirements

- Product must be fungible (identical across manufacturers) - Harm must be widespread (many plaintiffs, many defendants) - Identification must be genuinely impossible (not merely difficult) - Defendants joined must represent a substantial share of the market

Joint and Several Liability

When multiple tortfeasors cause an indivisible injury (one that cannot be apportioned), each defendant is liable for the FULL amount: - Plaintiff can collect 100% from any single defendant - That defendant may seek contribution from other tortfeasors - Modified in many jurisdictions by comparative fault statutes

Baby Bar Connection

Cause in fact appears in virtually every negligence essay. The key analytical points: - State the but-for test clearly - Apply it to the specific facts (don't just define it) - If concurrent causes exist, switch to substantial factor - Always distinguish cause in fact from proximate cause — they are separate elements requiring separate analysis