After a review of the record and of the parties’ submissions, we bypass the issue of appellate jurisdiction, see United States v. Woods, 210 F.3d 70 (1st Cir.2000), as it appears on this record that appellant most likely mailed his notice of appeal from prison within the adotted time; and we affirm the denial of appellant’s motion filed pursuant to Fed.R.Crim.P. 6(c).
Appellant seeks to challenge the institution of this prosecution by arguing that he was not properly indicted by a vote of at least 12 grand jurors, as required by Fed.R.Crim.P. 6(f). Federal Rule of Criminal Procedure 12(b)(1) requires that any challenge to the institution of a prosecution be raised pretrial; appellant’s challenge comes ten years too late. The failure to raise a timely challenge to the institution of the prosecution constitutes a waiver of that chadenge; and waiver will only be excused upon a showing of cause. See Fed.R.Crim.P. 12(f). This court reviews a refusal to grant relief from waiver under Rule 12(f) for an abuse of discretion. United States v. Santos Batista 239 F.3d 16, 20 (1st Cir.), petition for cert. filed, (U.S. May 7, 2001) (No. 00-10302); United States v. Bashorun, 225 F.3d 9, 14 (1st Cir.2000). Relief from waiver under Rule 12(f) is a “single nar*11row exception” which is “rarely granted.” Santos Batista, 239 F.3d at 19.
Appellant’s submissions wholly fail to show cause for his failure to raise this challenge before his trial, and given this failure and the passage of time, we see no abuse of discretion in the lower court’s denial of the motion.
Affirmed. 1st Cir. Loc. R. 27(c).