Short answers, pulled from the story.
The criminal justice system consists of three main parts: law enforcement agencies (usually the police), courts and accompanying prosecution and defense lawyers, and agencies for detaining and supervising offenders, such as prisons and probation agencies.
The Metropolitan Police in London, established in 1829 by Sir Robert Peel, is commonly recognized as the first modern police force. In the United States, Boston established its police department in 1838, followed by New York City in 1844.
August Vollmer, who served as police chief in Berkeley, California, established a criminal justice program at the University of California, Berkeley in 1916, marking the beginning of criminal justice as an academic discipline.
Plea bargaining is a practice used in the United States and some other countries that allows the accused to plead guilty, nolo contendere, or not guilty in exchange for a reduced punishment or diversion program, often when the prosecution's case is weak. Many nations do not permit plea bargaining, arguing it coerces innocent people into pleading guilty to avoid harsher penalties.
By 1950, criminal justice students in the United States numbered fewer than 1,000. The Law Enforcement Assistance Administration, created in the late 1960s, funded criminology research, and by 1975 student enrollment had surpassed 100,000. By the 1970s, 729 academic programs in criminology and criminal justice existed across the country.
Under pressure from a group of Quakers, Pennsylvania revived 17th-century correctional reforms toward the end of the 18th century that forbade torture and replaced corporal punishment with jails and prisons. These reforms led to a marked drop in Pennsylvania's crime rate. The Quaker movement in America is also commonly credited with establishing the idea that prisons should be used to reform criminals.