The Penumbra Problem: The Rise and Fall of the Little-Known Word that Protects Our Privacy

The U.S. Constitution is silent about a right to privacy, yet the Supreme Court determined in the 1965 reproductive rights case Griswold v. Connecticut, that such a right is inferred from the Bill of Rights. The reasoning in the landmark case hinged on an unexpected word—penumbra. The Court concluded, in other words, that the unmentioned right to privacy resides in the shadows of the amendments.

But this was not the first time penumbral imagery was used in legal writings, and its broader cu...