Persuasive authority: British case law in American courts

Not every source a court reads is one it must obey. The core distinction every self-represented litigant should master is binding vs. persuasive authority.

Binding vs. persuasive

Binding (mandatory) authority — a court must follow it: the applicable constitution and statutes, and precedent from a higher court in the same jurisdiction.
Persuasive authority — a court may consider it and be influenced by it, but need not follow it: decisions of other jurisdictions (including English courts), lower or coordinate courts, treatises, law dictionaries, and historical materials.

English cases as persuasive authority — M’Naghten’s Case

American courts still cite British decisions as persuasive authority, and some English rules were adopted so widely that they became the American standard. The classic example is M’Naghten’s Case, 8 Eng. Rep. 718, 10 Cl. & Fin. 200 (H.L. 1843) — decided by the British House of Lords, yet its test became the insanity-defense rule in many U.S. jurisdictions.

Under the M’Naghten rule, a defendant is not criminally responsible if, from a disease of the mind, he did not know the nature and quality of the act he was doing — or, if he did know it, that he did not know it was wrong. M’Naghten’s Case (H.L. 1843), as adopted across many U.S. states.

The lesson: an English case is not binding on an American court, but it can be highly persuasive — and once an American court adopts its rule, that American decision is the binding authority going forward, not the English case itself.