Can a criminal defendant knowingly and voluntarily waive the right to appeal a district court's yet-to-be-made errors as part of a plea agreement, and, if so, what are the limits on the validity and enforceability of such appeal waivers?

Petitioner Gregory Johnson’s appeal to the Fifth Circuit was wrongfully dismissed because the record cannot demonstrate a knowing and voluntary waiver of a sentence that constitutes a miscarriage of justice. The questions presented are: Can a criminal defendant knowingly and voluntarily waive the right to appeal a district court’s yet-to-be-made errors as part of a plea agreement, and, if so, what are the limits on the validity and enforceability of such appeal waivers? Relatedly, did the appeal waiver in Mr. Johnson’s case qualify for the so-called “miscarriage of justice” or other exception recognized by numerous appellate courts?