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Allan Pinkerton (1819–1884) -

Born in Glasgow, Scotland, Allan Pinkerton emigrated to the United States in 1842. There he created the Pinkerton National Detective Agency in the 1850s, which became the largest private law enforcement organization in the world at the height of its power. Among the agency's many successes was the infiltration in the 1870s of the secret society of Irish-American coal miners known as the Molly Maguires, and the tracking down of Old West outlaws, including Jesse James and the Wild Bunch, whose members included Butch Cassidy and the Sundance Kid.

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Kate Warne (1833–1868) -

Chicago-born Kate Warne was the only female agent Allan Pinkerton ever hired, and as such became the first woman detective in the United States. One of the country's least appreciated sleuths, Warne is credited among other triumphs with helping to uncover a February 1861 conspiracy to assassinate president-elect Abraham Lincoln in what became known as the Baltimore Plot. Image: Chicago History Museum, 1866

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Sir Robert Peel (1788–1850) -

British statesman Sir Robert Peel twice served as prime minister before founding the Metropolitan Police Service. As such, Peel is regarded as the father of modern policing in the United Kingdom. The Met, as it's informally called, is responsible for the prevention of crime and law enforcement in Greater London.

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August Vollmer (1876–1955) -

Berkeley, California police chief August Vollmer was an early 20th-century pioneer in the science of forensic investigations. He promoted the use of new technology for fighting crime, such as fingerprinting, polygraph machines, and crime laboratories. This, plus his crusade against police corruption and brutality, prompted many to describe him as the "father of modern policing."

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J. Edgar Hoover (1895–1972) -

J. Edgar Hoover is one of the most celebrated—and controversial—names in US law enforcement history. He served as the first director of the Federal Bureau of Investigation (FBI) for nearly 48 years, having previously ran the Bureau of Investigation, the FBI's predecessor. During his tenure, FBI agents apprehended or killed a number of notorious criminals, among them John Dillinger and George "Machine Gun" Kelly. Throughout the 1960s, however, the agency was criticized for its overt surveillance of Martin Luther King Jr. and the perceived insufficient attention given to the use of terrorism tactics by white supremacists.

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Eliot Ness (1903–1957) -

The name Eliot Ness is synonymous with The Untouchables, the team of law enforcement agents he led in Chicago throughout the Prohibition era. His greatest success was bringing down infamous mobster Al Capone. Ness' life and career has been depicted in various media, including television in the 1950's series 'The Untouchables' and, notably, in the 1987 Brian De Palma movie starring Kevin Costner as the incorruptible crimefighter.

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Izzy Einstein (1880–1938) and Moe Smith (1887–1960) -

The double detective act that was Isidor "Izzy" Einstein and Moe Smith saw the most arrests and convictions recorded during the early years of the Prohibition era. The two federal police officers were members of the elite Bureau of Prohibition and together were hugely successful in busting illegal speakeasys, very often working undercover in disguise.

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Frank Serpico -

Frank Serpico became one of the most famous police officers in the history of New York after he helped uncover endemic and widespread corruption within the NYPD. Shortly before he was due to blow the whistle against the department, Serpico was shot and wounded during an arrest attempt on February 3, 1971 in circumstances that suggest he was lured into a trap by disgruntled police officers. His story was retold in the acclaimed 1973 movie 'Serpico,' with Al Pacino portraying the brave and principled detective.

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Edward Egan (1930–1995) -

Eddie Egan was a New York City policeman who helped crack an organized drug smuggling operation in 1961 that later became known as the French Connection. Jimmy "Popeye" Doyle, Gene Hackman's character in the 1971 movie, is based on Egan, whose nickname was indeed "Popeye." Egan is pictured, wearing his trademark pork pie hat, escorting French national Jacques Angelvin out of a New York court in 1962 during the international narcotics ring investigation.

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Dave Toschi (1931–2018) -

Inspector Dave Toschi of the San Francisco Police Department was central to the infamous and still unsolved Zodiac killer case of the late 1960s and early '70s. Toschi, known for his meticulous investigation technique, was one of several officers taunted by the serial murderer, who detailed his crimes in letters and a cryptogram (pictured). Toschi's personal style was the model for the lead characters in 'Bullitt' (1968) and 'Dirty Harry' (1971).

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Lola Baldwin (1860–1957) -

Lolo Baldwin holds a special place in American law enforcement history as one of the first women to become a police officer in the United States. She was sworn in as such in Portland Oregon in 1908 and served the city until 1922. Throughout her policing career, Baldwin advocated crime prevention and favored reform over incarceration, and was especially vocal in promoting laws to protect women.

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Henry Fielding (1707–1754) -

Better known as a dramatist and novelist whose works include 'Tom Jones' (1749), Henry Fielding is nonetheless credited with cofounding the Bow Street Runners, London's first professional police force, created the same year as 'Tom Jones' was published.

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Elizabeth Fry (1780–1845) -

Born in Norwich, England, Elizabeth Fry is applauded for her efforts as a social reformer, and especially her fight for prison reform. She founded the Association for the Improvement of Female Prisoners in 1817 after witnessing the appalling conditions women and children were subjected to, including sexual exploitation, at London's Newgate Prison in 1818.

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Sir William James Herschel (1833–1917) -

William James Herschel is credited with inventing the fingerprint process, a technique he developed while working as a civil servant in India. Herschel realized that fingerprints were unique and permanent, and fingerprinting could be used to identify criminals and prevent impersonation.

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Alphonse Bertillon (1853–1914) -

French police officer Alphonse Bertillon researched and applied the anthropological technique of anthropometry to law enforcement— in other words, the use of physical measurements to identify criminals by recording the physical properties of the human body, primarily dimensional descriptors of body size and shape. The mug shot is the most obvious application of the technique, demonstrated here by Bertillon himself as a self portrait.

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William J. Burns (1861–1932) -

Baltimore-born William J. Burns began his career as a private investigator and later enjoyed considerable success after founding the William J. Burns International Detective Agency in 1909. An honest man of impeccable integrity, Burns was later accepted into the United States Secret Service, a position that eventually led to his appointment in 1921 as director of the Bureau of Investigation (forerunner of the FBI). His reputation was somewhat tarnished when he was forced to resign from the Bureau in 1924 because of his role in the so-called Teapot Dome scandal, which centered on the secret leasing of federal oil reserves by the secretary of the interior, Albert Bacon Fall.

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William J. Flynn (1867–1928) -

A contemporary of William J. Burns, William J. Flynn was the director of the Bureau of Investigation, from 1919 to 1921. Flynn cuts his teeth as a New York City lawman, which pitted him against early incarnations of the American Mafia, and especially feared mobster Giuseppe Morello. Flynn was instrumental in putting together the case that eventually led to Morello being convicted of counterfeiting. Image: Library of Congress

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Edith Smith (1876–1923) -

Edith Smith was a volunteer with the Women's Police Service when she was appointed as the first female police constable in England with full  power of arrest. Stationed in Grantham in Lincolnshire, her duties were specifically geared towards cases involving women and especially sex workers, the numbers of which she tried to reduce during the First World War after an army base was established near the town. She died in 1923 from an overdose of morphine, five years after leaving the force. Image source: Lincolnshire Police

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Samuel J. Battle (1883–1966) -

Samuel J. Battle was the first person of color to become a New York City police officer. He joined the force in 1911 and immediately suffered racial abuse from his fellow officers. That changed when he saved the life of a white colleague in the early 1920s, after which he was treated with the respect he deserved. He played a pivotal role in helping to quell the race riots in Harlem during 1935 and 1941, and later mentored Wesley Williams, the first black firefighter in the New York Fire Department. He retired in 1951.

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Ellis Parker (1871–1940) -

Ellis Parker was known as "America's Sherlock Holmes" for his astonishing success rate in solving cases, wrapping up 288 of the 300 or so major crimes he worked on. Parker was involved in the infamous Lindbergh baby kidnapping, a case that eventually led to his downfall after he allegedly directed two men to kidnap an attorney named Paul Wendel and torture him into a confession, believing he was responsible for the abduction. Wendel's "admission of guilt" was presented to the team prosecuting Bruno Richard Hauptmann, the man eventually convicted of the kidnapping and murder of the infant. Parker was exposed as the man behind Wendel's assault and false imprisonment and later jailed. He died in disgrace behind bars in Lewisburg federal penitentiary, Pennsylvania, in 1940.

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Marcel Guillaume (1872–1963) -

Paris police chief Marcel Guillaume was renowned as a shrewd and tenacious investigator who solved numerous high-profile cases during a long and distinguished career. Guillaume was involved in the 1933 Violette Noziere poisoning case, and led the investigation into the crimes of serial killer Henri Landru. He also tracked down the whereabouts of Berthold Jacob, a Jewish refugee kidnapped by a German agent and taken to Germany during the Second World War. Guillaume is pictured, second left, during the Berthold Jacob abduction case.

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Eugène François Vidocq (1775–1857) -

In a remarkable volte-face, French career criminal Eugène François Vidocq turned his back on a lifestyle characterized by wrongdoings to become a criminalist, eventually founding and becoming the first director of the crime-detection force Sûreté Nationale as well as the head of the first known private detective agency in the world.

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Ignatius Pollaky (1828–1918) -

Born in Hungary, Ignatius Pollaky became one of Victorian England's first and best-known private investigators. Known as "Paddington" Pollaky, he worked with the Metropolitan Police Service specializing in intelligence on foreign nationals living in Britain and advocating alien registration. Image: Faustin Betbeder, 'Figaro's London Sketch Book of Celebrities' (1874)

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Alice Clement (1878–1926) -

Milwaukee-born Alice Clement was sworn into the Chicago police department in 1909, and became a detective with the force four years later. In a famed investigation, Clement remained unconvinced that the death of a young woman from suspected typhoid was anything but. She later found out that the victim had in fact been poisoned as part of a plot hatched by the woman's aunt, who stood to gain financially from her niece's passing. Image: Chicago Examiner, 1915

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William E. Fairbairn (1885–1960) -

William Fairbairn was a British Royal Marine and police officer stationed in Shanghai in the early 20th century. In those days, Shanghai was one of the most dangerous cities in the world. To counter this lawlessness, he organized and headed a special anti-riot squad—essentially one of the world's first SWAT teams. Later, together with fellow firearms expert Eric A. Sykes, he designed the famous Fairbairn-Sykes fighting knife, or 'commando' knife, a stiletto-style fighting dagger used by British Special Forces in the Second World War. Image: National Park Service (NPS)

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Benjamin Ward (1926–2002) -

When Benjamin Ward was sworn in by New York mayor Ed Koch as the city's 34th police commissioner on January 5, 1984 (pictured), he became the first African American to hold that position. Ward began his career in 1951 as a patrolman in Brooklyn, and faced discrimination from both white residents and white fellow cops. His rise through the ranks was remarkable, culminating in that historic day in 1984.

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Jack Slipper (1924–2005) -

Detective Inspector Jack Slipper of the Metropolitan Police was affectionately known as "Slipper of the Yard" (referring to Scotland Yard). He led the investigation into the Great Train Robbery of 1963, and famously tracked down Ronnie Biggs—one of the escaped criminals involved in the heist—to Brazil.

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Jay J. Armes -

Private investigator Jay J. Armes began his career in Hollywood, appearing in movies and television shows, before starting his own private investigation agency in El Paso 1958. Armes lost both hands in a childhood accident and was fitted with prosthetics limbs, but his disability had little impact on his ability to solve numerous cases, most famously tracking down Marlon Brando's son Christian, whom he found after the boy had been kidnapped by his mother Anna Kashfi in 1972 (Armes is pictured being interviewed about the case).

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Kiran Bedi -

A former national tennis champion, Kiran Bedi holds the distinction of becoming the first woman in India to join the officer ranks of the Indian Police Service (IPS), in 1972. In her 35 years' of service, Bedi clamped down on bootlegging, sexual assault, and institutional corruption in Delhi and elsewhere during a period of intense political volatility. She retired in 2007 as Director General, Bureau of Police Research and Development. 

Sources: (History) (Britannica) (FBI) (Smithsonian Magazine) (ABC News) 

See also: Milestone moments in global women's history

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