The American system of criminal justice and investigations stem from English common law and practice, which advised colonial governments and gave rise to subsequent systems in the United States. In fact, the standing police force that most Americans take for granted did not always exist. Early Americans, like the English before them, were averse to the concept of a government-sponsored standing police force that could at any time be authorized to strip citizens of their rights and liberties. The current method of law enforcement, from apprehension to pre-trial investigations, also owes its roots to the English.
The first professional, paid American police forces started in the early seventeenth centuries: first in Boston in 1631 and about fifteen years later in New Amsterdam. Known initially as watchmen and later as constables, the officers did not enjoy the same level of responsibility or the same role in society as modern police. The role of watchmen and that of detective was firmly delineated. However, as the colonies expanded and later the nation grew, the need for more firmly established public systems and institutions evolved. One of the most significant of those institutions was the formalized criminal justice system. Sheriffs in the Western territories of the United States were responsible not just for the apprehension of criminals but also of straddling the interface between law enforcement and politics. "Law men" watch for when laws are broken, have the power and resources to investigate crimes and gather evidence, and present that evidence to the judiciary.
The formal criminal justice system depended on effective criminal investigations. Investigations help to legitimize the police force, placing the burden of proof on law enforcement in criminal cases. The idea that an individual is innocent until proven guilty, which derives directly from British law, has necessitated systematic criminal investigations.
However, law enforcement has also played critical roles in creating and enforcing social norms and also in achieving political objectives. The Pinkertons started off as a private protection service, which later morphed into a means of infiltrating groups or apprehending individuals for political purposes. Police investigations prior to the 20th century had a high potential for corruption ("History of Law Enforcement" n.d.). During the time of the Pinkertons' peak…