located at the Federal Law Enforcement Training Center in Charleston, South Carolina. Generally, U.S. probation officers investigate an offender's personal and criminal history for the court prior to sentencing and then may supervise defendants who have been sentenced to probation but not to a term of incarceration (unless the conditions of probation are violated). They may also serve arrest warrants, and can perform any other function assigned by the federal court. To date, four U.S. probation officers have died in the line of duty. State Most U.S. states employ parole officers via their department of corrections to supervise offenders that have served a prison term and have subsequently been paroled, or released from prison under supervision. This decision is commonly made after the review and consideration of an inmate's case by a warden, parole board or other parole authority. Parolees serve the remainder of their prison sentence in the community, which in some cases, is for life. However, some jurisdictions have modified or abolished the practice of parole and instead give post-release supervision obligations to a community corrections or offender rehabilitation specialist; often generically if imprecisely referred to as a probation or parole officer. Violations of parole are investigated by parole officers, and responses to violations vary by state and jurisdiction. For the most extreme violations, parole officers will revoke an individual's parole and return the offender to prison. Other jurisdictions have expanded the parole officer's duties to include post-incarceration supervision under special sentencing, such as convictions requiring sex offender registration. They may also supervise, with specialized conditions, individuals convicted of DUI, drug offenses, and domestic violence. In 2011, almost 1.1 million people were on parole in the United States. This was up from 2001, when almost 731,000 individuals were under parole supervision. Since 1980, the fastest growing population of offenders in the judicial system has been probationers, while prison populations have also continued to grow, with U.S. prisons now housing more than 1.6 million inmates. In some states, probation and parole officer duties are intertwined and officer's will supervise not only individuals serving community sentences after prison, but also individuals on probation as an alternative to incarceration. County Some jurisdictions operate probation services on a county level and officers are commonly employed by district, municipal, circuit courts, or by a sheriff's department. This includes both adult and juvenile probation services. These is commonly referred to as "pre-trial services". Some