Prior to 1960, law enforcement in Suffolk County was the responsibility of local towns and villages as well as the Suffolk County Sheriff's Office and the New York State Police. From the 17th century until well into the 20th century, many of these jurisdictions employed only part-time constables, who were usually appointed by local communities and paid to enforce court orders. Additional fees were paid for making arrests, serving warrants and transporting prisoners. Few of these constables had any formal law enforcement training, hours were often long and pay was low.

The New York State Police arrived on Long Island in 1917, and many towns and villages began forming their own small police forces soon thereafter. Training remained inadequate, however, and none of these forces were equipped to handle serious incidents or major crimes. Communication and cooperation between forces remained spotty.

The demographic transformation of the county following World War II, however, forced a change. The rapid suburbanization of those years brought with it a dramatic rise in traffic and crime that threatened to overwhelm the 33 separate law enforcement agencies then operating within Suffolk County. Voices demanding a unified county police force, similar to the one already operating in neighboring Nassau County, grew louder.

Following the passage, in 1958, of state legislation creating the county executive form of government, a referendum was held on the creation of a county police force. The five western towns — Babylon, Huntington, Islip, Smithtown and Brookhaven — voted in favor. The five eastern towns — Riverhead, Southold, Shelter Island, East Hampton, and Southampton — opted to retain their own police forces, and do so to this day, with the Suffolk County Police Department providing support and specialized services.

The towns that voted in favor thus agreed to turn over all their police functions to the new agency. In addition to traditional uniformed patrol services, the new agency agreed to provide: a Detective Bureau, a Communications Bureau, an Identification Bureau, a Central Records Bureau, and a police academy for training new officers.

All incumbent town and village police officers serving in those areas that voted to join the police district became members of the new department without further examination or qualification. In addition, state troopers serving on Long Island who so desired could request appointment to the new force. Criminal investigators in the district attorney's office were appointed the new detectives. The serving town and village police chiefs were typically appointed inspectors, deputy chiefs or assistant chiefs in the new department. The remaining positions were filled by competitive civil service examinations. The Suffolk County Police Department officially came into being on January 1, 1960 with 619 sworn members.

Today, the department has a strength of around 2,500 sworn officers, making it one of the largest police agencies in the country. In addition to officers, the department also employs 500 civilians, as well as nearly 400 school crossing guards. In 2006, the department announced it would be staffing its public information unit entirely with civilians, thus freeing more officers to return to patrol duty.

The department is headed by a civilian police commissioner, appointed by the county executive, and police headquarters are located in Yaphank. The department has a total of seven precincts. Four of the five towns are served by their own precinct, with odd-numbered precincts covering the south shore towns and even-numbered ones covering the north shore. The exception is the town of Brookhaven, whose sheer size (sprawling from Long Island Sound to the Atlantic Ocean) necessitated the establishment of two precincts, the 5th in Patchogue and the 6th in Selden (formerly Coram). Recently, because of population growth in the eastern part of Brookhaven and deployment problems from the existing station houses caused by Long Island's perpetually traffic-choked roads and highways, a third precinct (the 7th) was established in Shirley in the late 1990s.

Promotion to the ranks of sergeant, lieutenant, and captain are made via competitive civil service examinations. Promotion to the ranks of detective, deputy inspector, inspector and chief are made at the discretion of the police commissioner.

Title	Insignia
Police Commissioner
Chief of Department
Chief of Division
Assistant Chief
Deputy Chief
Inspector
Deputy Inspector
Captain/Detective Captain
Lieutenant/Detective Lieutenant
Sergeant/Detective Sergeant
Police Officer/Detective

The Suffolk County Police have investigated several well-known and notorious crimes and incidents, including the Amityville Horror murder case; the 1987 case of Richard Angelo, the so-called "Angel of Death;" the 1993 Katie Beers kidnapping;, the 1994 "Suffolk County Sniper" case and the Ted Ammon murder case. Suffolk ESU, K-9, Crime Scene and Aviation officers also participated in the recovery effort at the World Trade Center site in September 2001.

Recently, the Suffolk County Police and their interrogation methods have come under scrutiny due to the handling of the 1988 murder case of Seymour and Arlene Tankleff. Their only son, Martin Tankleff, was convicted of the crime after police extracted a false confession using deception. Tankleff was tried, found guilty and sentenced to 50 years to life for the murder of his parents. A recent appellate court decision has vacated the 1990 conviction and then Gov. Eliot Spitzer appointed Attorney General Andrew Cuomo as a special prosecutor to examine the handling of the case and all evidence collected to date.

In recent years, Suffolk officers (along with the Nassau County Police Department) have become well-known in the New York area for their exceptionally high rate of pay, especially as compared with the nearby New York City Police Department. In 2008, top pay for a Suffolk patrol officer is $97,958 annually, not including overtime, night differential and benefits, compared with $76,000 in New York City.

As a result of this disparity, numerous NYPD officers have left the city force and joined the Suffolk department. Typically, between one-third and one-half of the recruits in every Suffolk police academy class are former city officers. A police exam was administered to more than 29,000 applicants on June 9, 2007, which is considered one of the largest fillings for a police exam in the United States. The number is dwarfed however when compared to the 34,039 applicants who filed for one of three exams given by the NYPD in 2004.

Hiring issues have been contentious in recent decades, with the county coming under fire from African-Americans, Hispanics and other minorities claiming the hiring process discriminates against them. The U.S. Justice Department sued Suffolk for discriminating against women and minorities in police hiring in 1983. While denying any intentional discrimination, the county signed a consent decree three years later committing itself to increased minority hiring. The number of minority officers, however, has remained small. A cadet program aimed at smoothing the way onto the force for black and Hispanic young people was struck down in 1997 as unconstitutional reverse discrimination. On top of that, a well-publicized cheating scandal on the 1996 police exam further undermined confidence in the fairness of the hiring process. Controversy surrounding these issues has abated somewhat, but has not gone away entirely.

Six female officers sued the department for sex discrimination over its pregnancy policy and won a judgment from the federal Equal Employment Opportunity Commission (EEOC) in 2003. On June 14, 2006, a federal jury found that the police department discriminates against female officers by denying them access to limited duty positions, like working the precinct desk, during their pregnancies.

In a controversial move, Police Commissioner Richard Dormer in July 2006 announced that highway patrol and certain other units would undertake a pilot program whereby officers would record the race and/or ethnicity of drivers stopped for traffic violations. The purpose of the program, according to the commissioner, is to demonstrate that the department does not engage in so-called "racial profiling." The program has continued and is being expanded. While Dormer denies any racial profiling has taken place, he has refused to disclose the results.