Daily AncestorNon compos mentis
Non compos mentis is Latin for "not of sound mind"; in old records it marks a person the law judged insane or unable to manage his own affairs.
Courts used the phrase broadly for any serious loss of reason, whatever its cause, as distinct from mere weakness of mind. Later courts described it as an impairment severe enough that a person could not manage his own affairs or estate.
You meet it in insanity proceedings and in will contests, where heirs argue the testator was non compos when he signed. It is a legal finding, not a medical diagnosis.
As seen in a recordCounty court minutes, 1800s
Jury of inquest find that Jacob Pruett is a lunatic and non compos mentis, incapable of managing his estate
Sources
How to cite this page
Daily Ancestor. "Non compos mentis." Dictionary of Old Record Words. https://dailyancestor.com/dictionary/legal-land/non-compos-mentis. Last checked 2026-10-12.