The following is a California felony DUI case example.

ii)
People v. Snook (1997) 16 Cal.4th 1210  (DUI Multiple Conviction Enhancement Under Veh.Code § 23175(a))

            In Snook, the high court had to decide whether a lack of chronological sequence in hen prior DUI convictions do not warrant an enhanced penalty where the conviction for the first offense comes last, and whether if the increased is penalty is imposed, would violate the ex post facto clauses of the state and federal Constitutions. First, the high court noted that  DUI may be charged as a felony rather than a misdemeanor when the offense occurs within seven years of three or more separate DUI violations which resulted in convictions. (Veh.Code § 23175, subd. (a);  Id. at 1213.

            In interpreting the Legislature's plain language, the high court opined that "it is clear
the term "separate violations" means that the three or more DUI offenses which resulted in convictions must simply be different from the offense at issue in the present proceeding, and not
merely different from one another...the statute, by its terms, permits a DUI offense to be charged as a felony if the violation occurred within seven years "of" three or more other separate DUI
violations that resulted in convictions, thus allowing convictions for offenses that occurred before or after the offense underlying the present conviction to be used to trigger
an enhanced penalty. " Id. at 1216.

            In further finding that the ex-post facto constitutional provision is not violated where as here, "the increase in defendant's penalty in this case cannot be attributed to any change in law,
since section 23175(a) was effective at the time defendant committed the instant offense. Rather, it was defendant's own conduct that ultimately increased his punishment." Id. at 1221

            The high court held concluded that "the Legislature intended to punish repeat DUI
offenders with enhanced penalties, regardless of the order in which the offenses were
committed or the convictions obtained. Moreover, imposition of an enhanced penalty on a fourth DUI conviction for an offense predating the triggering violations does not contravene the
constitutional proscription against ex post facto laws, so long as the commission of the offense underlying the section 23175(a) charge occurred after the statute's 1984 amendment became
effective.  Id. at 1221-1222.