Also known as:onuses · onus probandi · burden of proof
Written by attorneys — see sources below.
A burden or obligation, especially the duty to prove a particular fact or proposition in litigation.
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How its tested
Common Examples
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Alternative Liability in Negligence
Olga O'Neill was struck by a rock while hiking near two quarries operated by separate companies. Both companies had been blasting negligently that day, but Olga could not identify which blast caused her injury. The onus shifted to each company to prove its conduct did not cause the harm.
Will Contest Burden Allocation
Opal Okoro petitioned to probate her uncle's will while a cousin sought a declaration of intestacy. Opal bore the onus of establishing due execution. The cousin bore the onus of proving lack of capacity or undue influence.
Odin Obeng suffered lung damage after exposure to asbestos from two different manufacturers over many years. One manufacturer sought to limit its liability by showing the harm could be apportioned. The onus fell on that manufacturer to prove the proper division of damages.
Gender Classification Scrutiny
Orlando Okafor challenged a state military academy's male-only admissions policy. The state bore the onus of supplying an exceedingly persuasive justification that the classification substantially advanced an important governmental objective.
Plaintiff's Causation Burden
Odilia Okamura sued a chemical plant claiming its emissions caused her respiratory illness. Because only one actor's conduct was at issue, the onus remained on Odilia to prove that the plant's emissions were the cause in fact of her harm.
Zoning Ordinance Justification
Olive Okafor and other college students challenged a village ordinance limiting occupancy to two unrelated persons. The Court applied rational basis review and upheld the ordinance, finding the measure did not improperly burden associational rights.
Village of Belle Terre v. Boraas416 U.S. 1 (1974)
Belle Terre is a village on Long Island’s north shore consisting of about 220 homes inhabited by 700 people. Its total land area is less than one square mile. The village has restricted land use to one-family dwellings and excludes lodging houses, boarding houses, fraternity houses, or multiple-dwelling houses.
The ordinance defines “family” as one or more persons related by blood, adoption, or marriage living and cooking together as a single housekeeping unit, exclusive of household servants. Up to two persons living and cooking together as a single housekeeping unit though not related by blood, adoption, or marriage shall be deemed to constitute a family.
Appellees the Dickmans own a house in the village. In December 1971 they leased it for an 18-month term to Michael Truman. Bruce Boraas later became a co-lessee. Anne Parish then moved into the house along with three others. These six individuals are students at the nearby State University at Stony Brook, and none is related to the others by blood, adoption, or marriage.
When the village served the Dickmans with an Order to Remedy Violations of the ordinance, the owners plus three tenants brought this action under 42 U.S.C. § 1983 seeking an injunction and a declaratory judgment that the ordinance is unconstitutional. The District Court held the ordinance constitutional. The Court of Appeals reversed. The Supreme Court noted probable jurisdiction.
During the litigation the lease expired and was extended. Anne Parish moved out. Thereafter the other five students left, and the owners now hold the home out for sale or rent, including to student groups.
It refers to a burden or obligation, most commonly the burden of proof that a party must carry on a particular issue.
When does the onus shift to the defendant in tort cases involving multiple actors?
The onus shifts when two or more defendants acted tortiously, the plaintiff suffered a single harm, and the plaintiff cannot identify which defendant caused the injury.
Who bears the onus in a will contest under the Uniform Probate Code?
Proponents bear the onus of proving due execution. Contestants bear the onus of proving lack of capacity, undue influence, or revocation.
How does the onus operate under intermediate scrutiny for gender classifications?
The government bears the onus of providing an exceedingly persuasive justification that the classification is substantially related to an important objective.
Does the onus always rest on the plaintiff to prove causation?
Yes, unless an exception such as alternative liability or apportionment applies, in which case the onus may shift to the defendants.
410 U.S. 113 (1973)
…or overbroad." A physician's abortion conviction was affirmed. In Thompson , n. 2, the court observed that any issue as to the burden of proof under the exemption of Art. 1196 "is not before us." But see Veevers v. State , 172 Tex. Cr. R. 162, 168-169, 354 S. W. 2d 161, 166-167 (1962). Cf. United States v. Vuitch , 402 U. S.…