Legal Definitions - Thayer presumption

A Thayer presumption is a legal principle that creates a temporary assumption of a fact in a legal case. When this type of presumption applies, one party benefits because the court will initially assume a certain fact is true without them needing to provide immediate proof. However, this assumption is easily overcome: the opposing party can rebut (disprove) it by presenting *any* credible evidence that contradicts the assumed fact. If such evidence is presented, the presumption "disappears" or "bursts," and the party who initially benefited from it must then prove the fact without the presumption's help.

Crucially, a Thayer presumption does not shift the ultimate burden of proof to the opposing party. The party who initially asserted the fact always retains the responsibility to prove their overall case, even if they temporarily benefited from the presumption.

• Scenario: Imagine a small business, "Bright Ideas Inc.," sends an invoice for services rendered to a client, "Innovate Solutions," via regular postal mail. Bright Ideas Inc. later sues Innovate Solutions for non-payment, claiming the invoice was sent and received. Innovate Solutions denies ever receiving the invoice.

  Application of Thayer Presumption: In many legal systems, there is a Thayer presumption that a letter properly addressed, stamped, and mailed was received by the addressee. In this case, Bright Ideas Inc. can present evidence that they correctly addressed, stamped, and mailed the invoice. This triggers the presumption, meaning the court will initially assume Innovate Solutions received it. Bright Ideas Inc. doesn't immediately need to provide direct proof of receipt (like a signed delivery confirmation). However, Innovate Solutions can rebut this presumption by presenting *some* evidence to the contrary – perhaps testimony from their mailroom staff that no such invoice was logged, or evidence of a postal service disruption during that period. Once Innovate Solutions presents this evidence, even if it's not definitively conclusive, the presumption "bursts." Bright Ideas Inc. then loses the benefit of the presumption and must present actual evidence (e.g., an email copy, a witness who saw the invoice arrive) to prove that Innovate Solutions indeed received the invoice. The ultimate burden of proving that the invoice was received remains with Bright Ideas Inc. throughout the case.

• Scenario: A married couple, David and Maria, have a child, Leo. Years later, during a contentious divorce proceeding, David suggests that Leo might not be his biological son, implying Maria had an affair.

  Application of Thayer Presumption: There is often a Thayer presumption that a child born to a married woman is the legitimate child of her husband. In this situation, Maria benefits from this presumption; the court will initially assume Leo is David's biological child without Maria needing to present immediate proof of paternity. However, David can rebut this presumption by presenting *some* credible evidence to the contrary. This could be a DNA test result that excludes him as the father, or even compelling testimony from a third party about Maria's relationship with another individual around the time of conception. Once David presents this evidence, the presumption disappears. Maria would then need to present her own evidence (such as a different DNA test confirming David's paternity, or testimony about their marital relations) to establish David's paternity. The ultimate burden of proving paternity, if it becomes a contested issue, would typically fall to the party asserting it (or the court might order further investigation), but the initial presumption that favored Maria would no longer apply.