Image copyright Reuters

When Robert Morgenthau passed away in New York, aged 99, he died where he had fought.

As one of America's longest-serving public prosecutors, he proved to be the scourge of mobsters, crooked politicians and white collar criminals.

The legendary lawyer oversaw some of the city's most sensational cases, from the murder of John Lennon to the jailing of the Central Park Five.

His career even inspired the writers of long-running American crime drama Law and Order.

By the time of his retirement at age 90, Morgenthau had become a New York institution.

But despite a life of wealth and privilege, he garnered a reputation for reform and upheaval in a city once mired by violent crime and corporate corruption.

"If you want people to have confidence in their government, you've got to show that people who have economic power or political power are not immune from prosecution," he told Bloomberg.

Morgenthau was born in 1919 to a wealthy, prominent New York family of German-Jewish origin.

His grandfather, Henry Morgenthau Sr., was a real estate tycoon and an ambassador under President Woodrow Wilson. Henry Jr., Robert's father, went on to serve as President Roosevelt's treasury secretary.

Growing up in Manhattan and on the family's apple orchard in upstate New York, Morgenthau enjoyed many of the privileges and connections afforded to the country's north-eastern elite.

He had a lifelong friendship with members of the Kennedy family, spent New Year's Eve with his father at the White House, and cooked hot dogs for Britain's King George VI and Queen Elizabeth during their stay at the home of Franklin and Eleanor Roosevelt.

After graduating from Amherst College, he enlisted in the US Navy in 1941 and served until the end of World War Two.

In 1944 he was left floating in the Mediterranean, scrambling for his life, after his ship was sunk by German forces.

"I made a deal with the Almighty," he later recalled. "If I got out alive, I'd devote my life to some form of public service. I'm still paying back."

At the end of the war, Morgenthau studied at Yale Law School and joined New York law firm Patterson, Belknap & Webb, where he worked for 12 years.

In 1960, he campaigned in the city for his childhood friend, John F. Kennedy. After Kennedy's election victory, he was appointed in 1961 as the US Attorney for the Southern District of New York, with a remit across Manhattan, the Bronx and six counties in upstate New York.

Image copyright Reuters Image caption As district attorney, Robert Morgenthau took aim at violent crime and Wall Street corruption

From early in his career he targeted organised crime and corporate corruption and set up the office's first specialist unit to investigate Wall Street. One of the unit's cases helped to set a legal precedent which, to this day, makes accountants liable for falsified financial reports.

In 1962, Morgenthau stepped down to run an unsuccessful bid for New York's gubernatorial race. He later returned to the role but left again in 1969, bowing to political pressure from President Richard Nixon.

Following a brief return to private practice, and a stint as deputy mayor, he joined the world of public prosecution again - this time, as District Attorney of New York County.

For the next 32 years, Morgenthau served as New York's top prosecutor.

When he was first elected in 1975, the city was in the midst of a crisis fuelled by government bankruptcy and rampant crime. That year, 648 people were murdered in Manhattan alone.

In his early years as district attorney, Morgenthau took aim at career criminals, crooked landlords and child pornographers, and promoted the use of modern investigation techniques like DNA testing.

He oversaw the expansion of the office's homicide team, and established new teams to deal with sex crimes and consumer affairs. As district attorney he also hired hundreds of black, Hispanic and female lawyers - along with dozens of Spanish-speaking interpreters - to help with investigations.

Image copyright Getty Images Image caption Thirteen years after helping to jail a group known as the Central Park Five, Morgenthau helped to exonerate the men after new evidence proved their innocence

Along with violent crime, Morgenthau continued his work against corporate corruption and the mafia, and hired dozens of accountants and specialised detectives.

Under his leadership, the district attorney's office oversaw several high-profile cases, successfully prosecuting mob bosses John Gotti and Anthony "Tony Ducks" Corallo.

His victories also included the 2005 conviction of L. Dennis Kozlowski, who stole more than $100m (£80.1m) from Tyco security firm whilst working as its chief executive.

In more off-beat cases, he convicted a mother and son of murder without a body being found, or a witness being used against them.

Beginning with 195 lawyers, Morgenthau's office grew to become one of the biggest in America, with over 500 lawyers and 700 staffers. Amongst its star-studded alumni are US Supreme Court Justice Sonia Sotomayor and New York Governor Andrew Cuomo.

But during his tenure, Morgenthau was criticised for hiring high numbers of Ivy League graduates and children of rich and influential families. Former members of his office also include John F. Kennedy Jr. and Cyrus Vance Jr., a son of the former US Secretary of State and Morgenthau's successor when he retired in 2009.

He was also lambasted over cases involving police brutality and racial bias, and some of his victories were later exposed as miscarriages of justice.

One that made international headlines was the conviction of five black and Hispanic teenagers over the beating and rape of a 28-year-old white woman.

Thirteen years later, in 2002, a serial violent offender named Matias Reyes confessed to the attack, saying he had acted alone. Morgenthau ordered a new investigation, and armed with the confession and fresh DNA evidence, the group, known as the Central Park Five, were exonerated.

"If only we had DNA 13 years ago," Morgenthau told the New York Times.

But despite his critics, the restless district attorney has been praised for taking on big business and organised crime, and credited with slashing murders in New York to some of the lowest on record.

After more than three decades in office, he told AP news agency that he had decided to retire because "I looked at my birth certificate, and I said, 'It's about time.'"