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 Delaware, an offer of proof is a procedural mechanism used during a trial to create a record of evidence that the court has deemed inadmissible. This is done outside the presence of the jury, typically after an objection to the evidence has been sustained by the judge. The purpose of an offer of proof is to preserve the excluded evidence for appellate review, allowing the appellate court to understand the context and potential impact of the evidence that was not presented to the jury. On the other hand, a bill of exception, or formal bill of exception, is a more antiquated procedure that was historically used to document objections to evidence that was excluded without an offer of proof during the trial. This would allow the appellate court to review what the evidence would have been, despite it not being part of the trial record. Modern rules of appellate procedure have largely replaced formal bills of exception with more streamlined processes for preserving a record for appeal, but the concept remains as a means to ensure that a party's rights are protected when evidence is excluded.