Donald Trump drew attention to one of the US president's most controversial powers with a final flurry of eyebrow-raising pardons, with the possibility raised that he might also pardon himself.

Here are six things to know about this presidential prerogative.

King of America

Pardons date back to Anglo-Saxon England when boiling, burning and drowning in a quagmire were common sentences for crimes.

America's founding fathers were divided on whether they should adopt the royal English precedent.

Giving the president the power to forgive himself and his allies might tempt him into error, some argued.

Others insisted the risk was slight, since no person honoured with such high office would ever risk tarnishing their reputation...

Taking advantage 

Long before he left the White House, Trump tried to bleach out the stain of the Russia interference investigation by awarding clemency to five close allies including Paul Manafort and former general Michael Flynn, who had pleaded guilty to lying to the FBI over his Russian contacts.

He also absolved campaign consultant Roger Stone who had been sentenced to 40 months in prison on seven felony charges -- a gesture one Republican senator called "unprecedented, historic corruption". 

The United Nations also slammed Trump for granting full pardons to four Blackwater security guards convicted over the 2007 killing of at least 14 Iraqi civilians in Baghdad.

In good company

But he is by no means alone. 

President Gerald Ford pardoned his disgraced predecessor Richard Nixon in 1974 after the Watergate scandal, a move that re-opened debate on the power.

The 1990s saw president George H.W. Bush pardon six people involved in the Iran-Contra scandal.

His successor Bill Clinton wiped the slate for his half-brother who had been convicted of cocaine possession, and billionaire Democratic Party donor Marc Rich, a fugitive guilty of tax evasion.

Roosevelt holds record

When it comes to the most pardons, America's wartime and Depression leader Franklin D. Roosevelt beats the band.

He cleared nearly 3,000 individuals of wrongdoing, including many who had violated prohibition laws that banned the sale of alcohol after World War I.

Jimmy Carter pardoned Vietnam-era draft dodgers in a decision that affected some 200,000 people.

Barack Obama used his office to lighten penalties for hundreds of non-violent drug offenders sentenced under laws that disproportionately condemned black men to long stretches behind bars.

Righting wrongs 

The pardon has also being used as a way of righting or apologising for historical wrongs.

Trump used it to wipe away the stain on suffragist Susan B. Anthony who was arrested in 1872 for voting before women had obtained the right to do so.

He also issued another posthumous pardon to the black boxer Jack Johnson, who was arrested in 1912 for violating the racist "White Slave Traffic Act" by crossing state lines with his white wife-to-be Lucille. They fled to France but he was jailed on his return to the US.