http://www.truthinjustice.org/bargaining.htm
"The plea bargain was a prosecutorial tool used only episodically before the 19th century. ''In America,'' Fisher says, ''it can be traced almost to the very emergence of public prosecution -- and public prosecution, although not exclusive to the U.S., developed earlier and more broadly here than most places.'' But because judges, not prosecutors, controlled most sentencing, plea bargaining was limited to those rare cases in which prosecutors could unilaterally dictate a defendant's sentence. ''Not until the crush of civil litigation brought on by the explosion of personal-injury cases in the industrial era did judges begin to appreciate the workload relief plea bargaining promised.'' In other words, plea bargaining is arguably another outgrowth of late-19th-century industrialization. "