The main purpose of Welfare and Institutions Code section 707 is the determination of fitness or unfitness for juvenile court. "Welfare and Institutions Code section 707 concerns the unfitness of certain juveniles to be treated as juveniles. Subdivision (b) sets forth a list of offenses for which certain juveniles will be presumed unfit to be adjudicated as juveniles." (People v. Neely (2004) 124 Cal.App.4th 1258, 1263.) "A brief review of the challenged procedure will be helpful. Juvenile court jurisdiction attaches in cases in which the defendant is 'under the age of 18 years when he violates any law of this state' . However, if the defendant is aged 16 years or older at the time of the offense, the district attorney may move to have the minor tried as an adult.If the district attorney so moves, the juvenile court conducts a fitness hearing to determine if the minor is 'amenable to the care, treatment, and training program available through the facilities of the juvenile court.'The probation officer is required to file a report on the minor's 'behavioral patterns and social history'; the minor and the district attorney may submit other relevant evidence. In reaching its decision the court must evaluate the following criteria: '(1) The degree of criminal sophistication exhibited by the minor. (2) Whether the minor can be rehabilitated prior to the expiration of the juvenile court's jurisdiction. (3) The minor's previous delinquent history. (4) Success of previous attempts by the juvenile court to rehabilitate the minor. (5) The circumstances and gravity of the offense alleged to have been committed by the minor.' "Ordinarily, the burden of proving unfitness is on the prosecution.But if the minor is charged with certain felonies enumerated in Welfare and Institutions Code section 707(b), he is presumed to be unfit for juvenile court treatment and must shoulder the burden of proving that he is a fit and proper subject under the five criteria listed above." (Ramona R. v. Superior Court (1985) 37 Cal.3d 802, 804-805.) Penal Code section 1185, in relevant part, states: "A motion in arrest of judgment is an application on the part of the defendant that no judgment be rendered on a . . . verdict of guilty. . . . It may be founded on any of the defects in the accusatory pleading mentioned in Penal Code Section 1004, unless objection has been waived by a failure to demur, and must be made and determined before the judgment is pronounced." Here, defendant demurred early in the case challenging the court's jurisdiction on the grounds that he committed the offenses when he was a minor. Thus, the issue of his entitlement to a fitness hearing prior to sentencing was properly before the court.