Answer to Question 1
Plea bargaining benefits the prosecutor because it provides him or her with a greater ability to dispose of a busy case load. District attorneys are often faced with limited resources and, as such, cannot prosecute every case that comes before them. Specifically, a district attorney may opt to pursue charges on cases that have a highly public element or are likely to result in guilty convictions.
Defense attorneys also benefit from plea bargaining. Public defenders, who are the most common type of counsel in criminal trials, face resource constraints similar to those of prosecutors. Plea bargaining benefits public defenders by allowing quick disposition of cases it also allows them to focus on cases that they perceive as being worthy of trial.
Plea bargaining benefits the defendant perhaps more than the prosecutor or the defense attorney; the obvious reason for this is that the defendant generally receives a lesser sentence (or charge) as a result of plea bargaining.
Answer to Question 2
One of the earliest reported cases addressing plea bargaining was decided in the early 1800s. In that case, Commonwealth v. Battis, 1 Mass. 95 (1804), a court was hesitant to permit a guilty plea by a defendant charged with a capital crime.
Following Battis, other cases involving some degree of plea bargaining were reported.
One court's opinion focused on a Michigan statute that set forth specific requirements necessary for a valid guilty plea. The Court expressed concern that some of what could be called plea bargaining was taking place without the approval of the courts (Edwards v. People, 39 Mich. 760 1878). Plea bargaining became even more common in the early to mid-1900s. Many states had, by then, impaneled commissions to study the workings of their criminal justice systems.