An offer of proof—also known as an informal bill of exception—is a procedure available during trial for the presentation of evidence the trial court has excluded. An offer of proof is made outside of the jury’s presence and often after the judge has sustained an objection to the admissibility of the evidence.

A bill of exception—also known as a formal bill of exception—is a procedure that allows a party to complain on appeal about evidence that would not otherwise appear in the trial record (because there was no offer of proof made at trial) by detailing the evidence (testimony, etc.) that would have been offered if the trial court had allowed it.

In Michigan, an offer of proof is a procedural tool used during a trial when the court excludes evidence. This process allows the attorney to create a record of the evidence that they believe should be admitted, which is done outside the jury's presence. The purpose of an offer of proof is to ensure that the appellate court is aware of the excluded evidence when reviewing the trial court's decision, in case the exclusion is claimed to be an error on appeal. On the other hand, a bill of exceptions is a more formalized record that captures what the evidence would have been if it had been allowed by the trial court. This is used when no offer of proof was made at trial, and it serves to inform the appellate court of the nature of the excluded evidence. Both procedures are important for preserving issues for appeal regarding the admissibility of evidence. Michigan court rules and case law provide the framework for these procedures, and attorneys must follow specific steps to ensure that the appellate courts consider their arguments regarding excluded evidence.