During a hearing to contest an International Extradition, the defense may seek to introduce 'explanatory' evidence that tends to show why the Government's case is not supported by a sufficient factual basis. This standard does not permit the defense to introduce any evidence that contradicts the Government's evidence of 'guilt' or 'innocence'. The United States Supreme Court interprets this distinction as permitting the introduction of evidence that explains the testimony of the government's witnesses - to show that there is not a sufficient basis to establish 'probable cause'; but does not permit evidence that calls into question the guilt or innocence of the person who is being extradited. In essence, the difference between admissible and inadmissible evidence is that the former is evidence that is rebutting probable cause, while the latter is a defense of the charge.

There are several federal court rulings that deal with explanatory evidence; however, no common pattern emerges from the decisions. The rulings range from allowing in very little explanatory evidence, to allowing so much that the hearing borders on a mini-trial. The newer court decisions focus on the introduction of evidence that can dispute probable cause, creating a very narrow line between evidence that actually disputes probable cause, and evidence that is merely contradictory or attempts to assert a defense. Under these cases, evidence that tends to 'obliterate' probable cause should be permitted.

Several types of information are often admissible, for example; in bank fraud cases the courts often allow the introduction of more records, or an explanation as to why the transactions are not fraud. Again, evidence of this type cannot dispute the prosecutions evidence; however, the defense can show that the prosecution does not have the entire picture, or that they are not correctly interpreting the facts. Alibi evidence might be admissible, but it would be held to a high standard, and would have to be stated in such a way that it is being used to 'obliterate' probable cause for the extradition. This type of evidence would have more weight if the alibi were something dramatic, such as the person being in a different country, or in another continent when the offense occurred.

The federal magistrate judge who hears the extradition has a significant amount of leeway in deciding what evidence to allow into the proceedings. This is an important consideration, as the only way to appeal the ruling of the magistrate judge is to initiate a Habeas petition in federal district court. The discretion of the magistrate judge in determining what evidence to admit is almost never overturned on these matters; therefore, if the evidence can be introduced in such a way that it sways the magistrate, then it would likely withstand any appeal by the government, or by the country trying to extradite the client.