From colonial times until the early 20th century, there was no separate legal system  for juveniles.  Youth over  the age of 14 were automatically deemed legal "adults" while those under 7 were  "infants" and exempt due to their ostensible failure to formulate criminal intent. Between the ages of 7 and 14, efforts were made to discern such intent and the doctrine of "malice supplies the age" operated.
As social scientists began to treat adolescence as a distinct development period and Progressive reforms gained political sway, states began to rethink the harsh treatment of juveniles and argued for a separate system  that would provide parental like guidance  with rehabilitative goals..
The child savers' advocacy resulted in the establishment of the first juvenile court in Cook County, Illinois, in 1899. The court was established under the British legal doctrine of parens patrae -- "the State as parent" -- which was interpreted to mean that it was the state's duty not only to protect the public interest in juvenile offender cases, but also to intervene and serve as the guardian of the interests of the children involved. As opposed to the adversarial adult criminal system, where the state's role was to prosecute the offender, the juvenile court had a more benevolent mission: it was designed to be flexible, informal and to tailor to a juvenile's individual needs, with the ultimate goal of rehabilitation. The process was subject to strict confidentiality in order to avoid any unnecessary stigmatization of minors. Because its goal of rehabilitation was not considered to be punitive, the court had no due process protections, and had jurisdiction over both criminal and status offenders(a category which applies only to minors and includes offenses such as vagrancy and truancy.) Judges played a paternal role, and were afforded tremendous discretion in order to achieve the goal of individualized rehabilitative justice. By 1925, 48 states had established a juvenile court system, which operated quietly until mid-century.
By the mid-20th century, it had however become clear that juvenile system was simply a miniature  adult system of punishment and imprisonment without due process protections. In a series of cases -- Kent, in re Gault and Winship, the Supreme Court granted due process protections to juveniles while acknowledging that , despite rehabilitative ideals, juvenile justice was indeed a legal system with had the power to detain and in essence deprive youth of life liberty and property. These case did offer jueviles additional legal protections including formal hearings when facing waiver to criminal court; protection against self-incrimination; the rights to notice of charges, counsel, and cross-examination of witnesses; and adherence to the "proof beyond a reasonable doubt" judicial standard. Still, they did not offer any protections for juveniles waived into the adult system who faced life imprisonment and even execution until this practice was finally banned in 2005.
Over the past 40 years, the juvenile justice system has shifted sharply from its’ original rehabilitative, therapeutic and reform goals. While the initial Supreme Court rulings of the 1960s sought to offer juveniles some legal protections n what was in fact a legal system, more recent changes have turned the juvenile justice system into  a “second-class criminal court that provides  youth with neither therapy or justice.” Since the 1980s, legislators, in a pattern that parallels their response to "super predator myths", adult crime and sentencing, have enacted a series of increasing tough policies with respect to juvenile offenders. These include a plethora of new policies that ease the transfer of juveniles into adult court via certification or related net –widening practices.
Juvenile justice policy has literally re-converged with the adult criminal justice system. State legislators began to facilitate the ease of transfer of juveniles directly into the adult criminal justice system.  This process - variously called transfer, certification, remand, or bind over - is entirely regulated by the states.  As Griffin (2008) observes,
“A total of 31 states made substantive changes to their laws governing the criminal prosecution and sentencing of juveniles during the five-year period from 1998 to 2002. In general, the changes tended to expand the reach of these laws. But legislative activity was less frequent and less dramatic during the 1998-2002 period (especially during the latter years of the period) than in the years 1992 through 1997, when nearly all states took significant steps to toughen up their laws in this area, and many rewrote them completely.”
All states allow adult criminal prosecution of juveniles under some circumstances. The most common mechanism for transferring juveniles to adult criminal court is the judicial waiver. Since the Kent decision of 1966, states have been required to formalize the process by which this transfer occurs. There are 46 states that authorize or require juvenile court judges to waive jurisdiction over individual cases involving minors, so as to allow prosecution in adult criminal courts. What has changed more recently is the ease of waiver, the lowering of the age at which juveniles maybe refereed to adult courts in many states, and the expansion of options that allow for simultaneous juvenile and adult court jurisdiction.

 Many states now have statutes that exclude certain serious, violent, and/or repeat offenders from the juvenile court's jurisdiction. In many jurisdictions, referral to adult court is now mandatory, giving the juvenile court no role except that of making the probable cause determination. In all,the laws of 38 states dictate adult criminal handling of some categories of juvenile offenders, either by way of statutory exclusion, mandatory waiver, or both. In a case covered by a statutory exclusion, the juvenile is tried from the beginning "as an adult"--that is, proceeded against (by information, indictment, or otherwise) in the criminal court that would have had jurisdiction over the same offense if it had actually been committed by an adult.
The past two decades has also seen several states lower the age at which a juvenile can be referred to adult court. It should be noted that 23 states have no lower age limit, meaning that youth as young as 8 sentenced as adults. The remaining states specify ages between 10 and 15.

One new development in the juvenile court systems isblended sentencing, where the jurisdiction of the juvenile court is extended past age 18 and both juvenile and stayed adult criminal court sentences are imposed. 26 states have some form of blended sentencing as an option; often, it is accompanied by an inclusion of juvenile convictions in adult criminal history scores. This has the effect of widening the net and increasing the adult criminalization of juveniles who do not meet the criteria for waiver, as well as their potential sentence length. In discussing Minnesota’s Extended Juvenile Jurisdiction (EJJ), Podkopacz and Feld (2001) write:
“Although the legislature intended EJJ to provide judges with a stronger juvenile treatment alternative to waiver, the law instead had a substantial “net-widening” effect; judges continued to waive the same numbers and type of youths that they had transferred previously and revoked the probation and executed the adult sentences of nearly one-third of EJJ youths, many of whom were younger and first-offenders. Most of those youths, judges previously had decided should not be waived and many of them had their probation revoked for technical violations rather than new offenses.”
One of the most extreme outcomes of transfer to the adult system is the sentencing of juveniles to life without parole. Currently over 2000 juveniles are serving such a sentence. Nearly 25% of these youth are in the states of Louisiana and Florida ( see interactive state map). Although the Supreme Court recently struck down juvenile life sentences without parole for non-homicidal offenses inGraham v Florida, the bulk of youth sentenced will not be impacted as felony murder is the common common conviction offense in these cases.
The distinction between the school system via the school to prison pipeline, the juvenile justice system and adult criminal justice is increasingly blurred. Youth of color are increasingly at risk for arrest for a multitude of serious offenses as well as at risk for adult prosecution. Critics of these policies changes charge that this is no mere coincidence. The  age of mass incarceration and the prison industrial complex calls for the continual replenishment of the ranks of the imprisoned, and it is most often youth of color that are most often selected to fill that onerous role.
Sentencing juveniles to adult time comes at a high price. The practice flies in the face of science, compassion and desired criminal justice outcomes. The impact is nothing but negative - of course for the youth involved but also for society at large. A recent report from the Campaign for Youth Justice (pdf) outlines the  down-side of this practice:
Teen Brains Are Not Fully Developed During adolescence, the brain undergoes dramatic changes to the structure and function of the brain impacting the way youth process and react to information. The region of the brain that is the last to develop is the one that controls many of the abilities that govern goal-oriented, “rational” decision-making, such as long-term planning, impulse control, insight, and judgment.
The juvenile justice system is based on this science and provides troubled adolescents with mentors, education, and the guidance to help most of them mature into responsible adults. In contrast, warehousing minors in the adult system ensures that they will not have guidance from responsible adults or have access to age-appropriate programs, services and punishment to help build positive change into their brains during this crucial developmental period.
Moving Juveniles Into The Adult System Costs States Millions With the current financial crisis, states across the country are exploring ways to decrease the costs of the justice system. When state policymakers have conversations about reforms to either the juvenile or adult criminal justice system, an issue that often gets forgotten is youth in the adult system. Some states see the juvenile and adult systems as interchangeable and seek to consolidate the two systems in an effort to save money. This is a very costly mistake for states as each high-risk youth diverted from a life of crime saves society nearly $5.7 million in costs over a lifetime.
The Juvenile Justice System Demands More Than the Adult Justice System The adult system is typically thought to be more punishment-oriented than the juvenile system, but the minor crimes that youth commit mean that the majority of youth are only given an adult probation sentence as well as a lifelong adult criminal record that makes it hard for them to get jobs in the future. In contrast, the juvenile justice system holds youth accountable for their crimes by placing more requirements on youth and their families. The juvenile justice system often requires that youth attend school, pay community and victim restitution, and receive the counseling, mentoring, and training they need to turn their lives around. The adult justice system completely fails those youth who would benefit from the services of the juvenile system by letting them “slip through the cracks.”
Most Youth in the Adult System Are Convicted of Minor Crimes The majority of youth held in adult prisons are not given extreme sentences such as life without parole, and 95% of youth will be released back to their communities before their 25th birthday. Unfortunately, by virtue of being prosecuted in the adult system these youth are less likely to get an education or skills training, and their adult conviction will make it harder for them to get jobs.
Youth Are Often Housed in Adult Jails and Prisons On any given night in America, 10,000 children are held in adult jails and prisons. State laws vary widely as to whether youth can be housed in adult facilities. Although federal law requires that youth in the juvenile justice system be removed from adult jails or be sight-and-sound separated from other adults, these protections do not apply to youth prosecuted in the adult criminal justice system. In fact, many youth who are held in adult jails have not even been convicted. Research shows that many never will. As many as one-half of these youth will be sent back to the juvenile justice system or will not be convicted. Yet, most of these youth will have spent at least one month in an adult jail, and one in five of these youth will have spent over six months in an adult jail.
While in adult jails or prisons, most youth are denied educational and rehabilitative services that are necessary for their stage in development. A survey of adult facilities found that 40% of jails provided no educational services at all, only 11% provided special education services, and a mere 7% provided vocational training. This lack of education increases the difficulty that youth will have once they return to their communities.
Youth are also in extreme danger when held in adult facilities. Staff in adult facilities face a dilemma: they can house youth in the general adult population where they are at substantial risk of physical and sexual abuse, or they can house youth in segregated settings in which isolation can cause or exacerbate mental health problems. Youth who are held in adult facilities are at the greatest risk of sexual victimization.   Keeping youth away from other adult inmates is no solution either. Isolation has devastating consequences for youth. In fact, youth housed in adult jails are 36 times more likely to commit suicide than are youth housed in juvenile detention facilities.
Prosecuting Youth in the Adult System Leads to More Crime, Not Less The U.S. Centers for Disease Control and Prevention and the Office of Juvenile Justice and Delinquency Prevention, youth who are transferred from the juvenile court system to the adult criminal system are approximately 34% more likely than youth retained in the juvenile court system to be rearrested for violent or other crime.
Youth Have Lifelong Barriers to Employment An adult conviction can limit a youth’s opportunities for the rest of his or her life. While most juvenile records are sealed, adult convictions become public record and, depending on the state and the crime, can limit a youth’s job prospects for a lifetime. Legal barriers for people with criminal records include:
• Most states allow employers to deny jobs to people arrested but never convicted of a crime;
• Most states allow employers to deny jobs to anyone with a criminal record, regardless of how old or minor the record or the individual’s work history and personal circumstances;
• Most states make criminal history information accessible to the general public through the Internet, making it extremely easy for employers and others to discriminate against people on the basis of old or minor convictions, for example to deny employment or housing; and
• All but two states restrict in some way the right to vote for people with criminal convictions.
Youth of Color Are Disproportionately Impacted by These Policies Trying youth as adults has negative consequences for all youth, but communities of color are particularly harmed by these policies. Youth of color are over-represented at all stages in the juvenile justice system, the disparities are most severe for youth tried as adults.
• While African-American youth represent only 17% of the overall youth population, they make up 30% of those arrested and an astounding 62% of those prosecuted in the adult criminal system. They are also nine times more likely than white youth to receive an adult prison sentence.
• Latino children are 43% more likely than white youth to be waived to the adult system and 40% more likely to be admitted to adult prison.
• Native youth are 1.5 times more likely than white youth to be waived to the adult criminal system and 1.84 times more likely to be committed to an adult prison.
Publications Both of these reports provide excellent background/context for the trends and policy impacts they document and detail.
State Trends: Legislative Changes from 2005 to 2010 Removing Youth from the Adult Criminal Justice System (2011) Campaign for Youth Justice, written by Arya Neelum.
From Time Out to Hard Time:  Young Children in the Adult Criminal Justice SystemA comprehensive look at how the United States treats pre-adolescent children, primarily 12 years of age and under, who are charged with serious crimes – and the severe outcomes for those children.  (2009) Lyndon B. Johnson School of Public Affairs, University of Texas, lead author Michele Deitch.
State Campaigns
Thanks to the Campaign for Youth Justice for this information related to relevant, ongoing state campaigns.
North Carolina
If your state isn’t listed above,here"> please go here  to see if there is a group actively working on reducing the prosecution of youth in adult court where you live.
National Campaigns
Thanks to the Campaign for Youth Justice for information on relevant national campaigns.
Go to this page on the CFYJ for more information on these campaigns:
Tell the U.S. Senate to Restore Juvenile Justice Funding
Urge the Appointment of a Permanent Administrator for the Office of Juvenile Justice and Delinquency Prevention
 Reauthorize the Juvenile Justice & Delinquency Prevention Act
Support the Family Justice Act
Demand that A&E (cable channel)Tell the Truth About "Scared Straight"