Defendant was charged with a prior “strikes” conviction. He made no allegation it was constitutionally invalid nor did he produce any evidence at the court trial on the prior. On its own initiative, the trial court found that the prosecution had failed to meet its burden of proof of the validity of the waiver of Boykin-Tahl (Boykin v. Alabama (1969) 395 U.S. 238; In re Tahl (1969) 1 Cal.3d 122) rights at the time of the plea, and thus found the prior “not true.” The prosecution is not required to prove the validity of the underlying plea as an element of the “truth of the prior conviction,” because such challenge can only be made under the procedures set forth in People v. Sumstine (1984) 36 Cal.3d 909 and People v. Allen (1999) 21 Cal.4th 909. Those cases require the defendant first to sufficiently allege that his Boykin-Tahl rights were violated in the earlier plea, and second to bear the burden of producing evidence of that assertion in a subsequent evidentiary hearing. Only after those two steps have been completed does the burden shift to the People to show compliance with Boykin-Tahl principles. Also, a “not true” finding of a prior conviction based upon the absence of proof of a Boykin-Tahl waiver is not an acquittal, and therefore the prosecution may appeal the court’s order effectively striking the prior conviction.