Also known as: post-hoc · post hoc ergo propter hoc
Written by attorneys · grounded in primary & secondary sources — see below
An analysis or justification formed after the relevant events have occurred. It frequently embodies the logical fallacy of assuming that because one event followed another the first caused the second.
Portia Price sued a university in federal court. The presiding judge had once served as a trustee negotiating with the university but learned of the connection only after judgment. The court of appeals vacated the judgment because the post hoc discovery of the disqualifying interest undermined public confidence in the judiciary.
Patricia Patel challenged a state abortion restriction. The state defended the law by citing health concerns that emerged only during litigation. The court rejected the defense because the post hoc rationale did not reflect the legislature's actual contemporaneous purpose.
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Pavel Petrov bought stock and later sued for fraud on the market. After the price dropped he executed an affidavit stating he had relied on market price. The court viewed the affidavit as a post hoc statement that could not reliably establish reliance at the time of purchase.
Prism Analytics invoked a House Report to limit supplemental jurisdiction. The report appeared after the statute's passage and contradicted the enacted text. The court refused to credit the post hoc legislative history as altering the plain statutory result.
Penelope Price sued officers who brought reporters into her home during an arrest. The officers later claimed the ride-along served legitimate law-enforcement purposes. The court dismissed those post hoc rationalizations because they did not reflect any recognized exception at the time of the search.
Pablo Perez challenged enforcement of a sodomy law that applied only to same-sex conduct. The state offered post hoc explanations that the selective enforcement protected public morals. The court found those explanations belied by the state's own prior actions and insufficient to justify the classification.
Post hoc analysis looks backward at actual results after notice has been given. Ex ante evaluation asks whether the notice procedure was adequate when viewed from before the events unfolded. Courts assess the constitutionality of notice procedures ex ante rather than through post hoc success rates.
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The justification must be genuine and not invented after litigation begins. Overbroad generalizations about the talents or capacities of men and women cannot supply an exceedingly persuasive reason when offered only as a post hoc rationalization.
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The fallacy assumes that because one event followed another the earlier event must have caused the later one. Legal opinions frequently label after-the-fact explanations as post hoc when they rest on nothing more than sequence.
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…sodomy; even though that prohibition is concededly unconstitutional with respect to heterosexuals; and even though the State's post hoc explanations for selective application are belied by the State's own actions. At the very least, I think it clear at this early stage of the litigation that respondent has alleged a…