A more thorough explanation:

The Thayer presumption is a legal concept that allows one party in a trial to present evidence to challenge a presumption made by the other party, without shifting the burden of proof. This means that the party against whom the presumption operates can try to prove that the presumption is incorrect, but they are not required to prove it.

For example, in a case where a person is accused of stealing a car, there may be a presumption that the person had the intent to steal the car if they were found in possession of it. The Thayer presumption would allow the accused person to present evidence to challenge this presumption, such as showing that they had a legitimate reason for having the car.

The Thayer presumption is commonly used in civil trials in federal court, and it is important because it allows both parties to present evidence and arguments to support their case, without unfairly burdening one party with the responsibility of proving or disproving a presumption.