is allowed only under compelling circumstances to achieve justice and to address errors of the most fundamental nature.

A writ of error coram nobis is a writ which is used to inform a court (usually an appeals court) of facts not on the record despite due diligence by the party filing the writ (the petitioner). It is usually considered extraordinary in nature. The state of Arkansas Supreme Court has explained how such a writ is allowed:

• A writ of error coram nobis is an extraordinarily rare remedy, known more for its denial than its approval.
• The writ is allowed only under compelling circumstances to achieve justice and to address errors of the most fundamental nature.
• The only reasons for issuing such a writ (in the case of Criminal Appeals) is "in one of four categories: (1) insanity at the time of trial; (2) a coerced guilty plea; (3) material evidence withheld by the prosecutor; or (4) a third-party confession to the crime that occurs during the time between conviction and appeal."
• Coram nobis proceedings are attended by a strong presumption that the original judgment was valid.
• Although there is no specific time limit for seeking a writ of error coram nobis, due diligence is required in making an application for relief; in the absence of a valid excuse for delay, the petition will be denied.
• With regard to seeking a writ of error coram nobis, due diligence requires that (1) the defendant be unaware of the fact at the time of trial; (2) he could not, in the exercise of due diligence, have presented the fact at trial; or (3) upon discovering the fact, he did not delay bringing the petition.
• The supreme court does not lightly overrule cases and applies a strong presumption in favor of the validity of prior decisions; as a matter of public policy, it is necessary to uphold prior decisions unless a great injury or injustice would result.
• A mere claim of newly discovered evidence in itself is not a basis for relief under coram nobis; the petitioner must show that a fundamental error occurred, such that the facts as alleged as grounds for its issuance are such that there is a reasonable probability that the judgment of conviction would not have been rendered or would have been prevented had the exculpatory evidence been disclosed at trial, not that the newly discovered evidence might have produced a different result had it been known to judge and jury.
• It is the petitioner's burden to show that a writ of error coram nobis was warranted; the supreme court would not undertake to reinvest jurisdiction in the trial court just for the purpose of allowing petitioner to conduct a "fishing expedition."

Echols v. Arkansas, 125 S.W.3d 153