The success of a defendant depends on a perfect case; his loss arises from some defect.

Explanation

(English-origin maxim.) A defendant prevails only when his case is without defect — a single flaw in the defense is enough to undo it, while success requires perfection at every point.

Where this applies

• A defendant wins a breach-of-contract case because his performance was flawless — every term was met — while the plaintiff's claim had a fatal procedural flaw.
• A homeowner defeats a code-enforcement action by showing perfect compliance with every regulation, while the city's case falls apart because of one overlooked exception.
• A company's defense in a patent case succeeds because every claim is addressed, but a single missed deadline by the opposing side dooms their entire case.