Definition
A Latin maxim of evidence and procedure meaning: "No one alleging his own turpitude is to be heard." The full form is typically rendered *nemo allegans suam turpitudinem est audiendus* — no person is to be heard (or credited) when relying upon his own wrongdoing or moral baseness as the foundation of a legal claim. The principle operates as a rule of preclusion: a party cannot build a case upon the premise of his own illegal, fraudulent, or grossly immoral conduct. Courts will refuse to lend assistance where the claimant's own turpitude is the necessary basis of the relief sought.
The maxim is closely related to — and often treated as a variant expression of — the equitable doctrine that one who comes into court must come with clean hands. It also intersects with the common law rule that a witness is not compellable, and historically was not permitted, to answer questions that would expose him to infamy or disgrace, a rule that has since been substantially modified by statute and rule in most jurisdictions.
Common Confusion
This maxim is frequently conflated with two related but distinct principles. First, *ex turpi causa non oritur actio* — "from a base cause no action arises" — covers similar ground in the context of illegality as a defense to contract claims, but is a substantive rule about the enforceability of agreements rather than a rule about who may be heard. Second, the clean hands doctrine in equity is the closest modern functional equivalent, but it applies specifically within the equitable jurisdiction and carries its own body of case law. A researcher treating all three as interchangeable will miss jurisdictional and doctrinal distinctions that matter in primary source research.
Why It Matters in Research
This maxim appears in historical sources primarily in its full Latin form with the terminal word *audiendus*, which is the operative term — it is the word that carries the procedural consequence (the party or witness is not to be heard). Researchers scanning historical indices or abridgments under "N" should look for *nemo* entries as a cluster; Latin maxims were frequently grouped together without cross-referencing to the underlying doctrines they supported.
The practical application of this maxim splits across at least two distinct legal contexts that historical sources do not always carefully separate: (1) the testimonial context, where a witness could formerly refuse to answer questions tending to expose his own infamy — a protection distinct from the privilege against self-incrimination; and (2) the pleading and claims context, where a party is barred from founding a cause of action on his own wrongful act. Confusing these two applications produces research errors, particularly when reading older English equity and common law cases alongside American authorities.
In American sources from the nineteenth century, the maxim is frequently cited in contract disputes involving illegal consideration and in cases where a party sought to enforce an agreement tainted by fraud the party himself committed. Researchers should note that the modern clean hands doctrine and the illegality defense in contract law have largely absorbed the substantive work this maxim once did explicitly. Modern opinions rarely cite the Latin; they apply the underlying rule without attribution. Tracing doctrine forward requires following those successor doctrines, not the phrase itself.
The Rapalje & Lawrence entry places this maxim within a sequence of *nemo* maxims, which is the standard organizational approach in nineteenth-century legal dictionaries. The surrounding entries — on a person not being compelled to sell property, on estoppel, and on losing property without one's own act or default — suggest the editors understood the maxim in the context of self-defeating claims broadly, not only in the testimonial sense.
Historical Dictionary Support
Rapalje & Lawrence treat this maxim as part of a catalogue of *nemo* principles, presenting it in compressed form alongside *nemo cogitur rem suam vendere etiam justo pretio* and *nemo contra factum suum venire potest*. The editorial arrangement implies a thematic connection: each maxim limits what a party may assert against his own prior conduct or position. The entry does not elaborate the doctrine at length, which is characteristic of the Rapalje & Lawrence approach to Latin maxims — citation and translation, with minimal analysis.
Older English sources, including Broom's *Legal Maxims* and Broome's treatment in equity texts, give this maxim somewhat more analytical attention, connecting it explicitly to the in pari delicto doctrine and to the clean hands rule in Chancery. What the historical dictionaries generally miss is the distinction between the testimonial application (the witness's privilege against questions going to infamy, which was a common law rule distinct from the Fifth Amendment privilege) and the substantive application (preclusion of claims grounded in the claimant's own wrong). That distinction matters considerably in practice and in reading older cases accurately.