A more thorough explanation:

After-discovered evidence, also known as newly discovered evidence, refers to evidence that existed during the original trial but was only discovered after the trial's conclusion. This type of evidence is mainly an issue in criminal proceedings and can be used as the basis for a motion for a new trial.

Courts use a four-part test to determine whether to grant a new trial based on after-discovered evidence. The court considers whether the new evidence:

1. Could not have been obtained before the trial's conclusion through reasonable diligence
2. Is not merely corroborative or cumulative
3. Will not be used solely to impeach a witness's credibility
4. Would likely result in a different verdict or lighter sentence if a new trial were granted

For example, if new DNA evidence or a confession from another suspect is discovered after a trial, it may be enough to warrant a new trial if it weakens the case against the defendant enough to create reasonable doubt about their guilt.

After-discovered evidence can also be used to challenge judgments in civil proceedings, such as foreclosure actions, under Rule 59 of the Federal Rules of Civil Procedure. However, changes in law or interpretations of the law are generally not accepted as after-discovered evidence.

Prosecutors who learn of new, credible, and material evidence that creates a reasonable likelihood that a convicted defendant did not commit the offense of which they were convicted must disclose the evidence or remedy the conviction under the model rules of professional responsibility.

In summary, after-discovered evidence is evidence that was not known or available during the original trial but is discovered later. It can be used to challenge a verdict or sentence in criminal or civil proceedings if it meets certain criteria and would likely result in a different outcome if a new trial were granted.