Although juries are considered "fundamental to the American justice system", not all persons accused of violating the criminal law are entitled to a trial by jury. For example, youths prosecuted as juvenile offenders have no right to have their case heard by a jury. Similarly, adult offenders charged with petty offenses enjoy no right to be tried by a jury. In fact, the Sixth Amendment to the Constitution guarantees the right to a trial by a jury of one's peers to only adults charged with a serious offense (a crime where, if found guilty, the offender could receive more than six months in jail or prison). Still, some state constitutions do guarantee a jury trial to anyone facing criminal charges, including petty crimes like traffic offenses. Today, juries vary slightly in their size, but the most common for criminal trials is 12 jurors. Please outline the jury selection process from start to finish, being sure to include the differences between a peremptory challenge and a challenge for cause.