MBE Rules · Torts
Actual cause (cause-in-fact)
The rule
But-for: but for defendant's act, the harm would not have occurred. Substantial factor: when multiple sufficient causes (concurrent or parallel) — each is a cause if each was a substantial factor. Alternative liability (Summers v. Tice): burden shifts to defendants when only one of several caused the harm.
In plain English
To show someone actually caused harm, you need to prove the harm wouldn't have happened without their action, or that their action was a major factor among several causes.
Worked example
A factory and a nearby farm both release chemicals into a river, killing fish. Even if the factory's discharge alone could kill the fish, it's still an actual cause because it's a significant part of the problem.
Memory hook
ACTUAL CAUSE: 'But-for' or 'Big Factor'. One act or many, if it tips the scales, it's a cause.
The trap
Students think: Any act that contributes is enough. Wrong, because trivial contributions don't count. The actual test is 'but-for' or 'substantial factor'.
How examiners test it
The MBE loves: two hunters, one bullet hits plaintiff. Question: who caused the harm? Trap: assuming both must be liable without shifting burden (Summers v. Tice).
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