Villain and victim: Former South Korean President Park Geun-hye (left) arrives for her trial at the Seoul Central District Court in Seoul. Photo/AP
PRESIDENTS and prime ministers who start wars still don't go to jail, but in democratic countries it is getting common to see presidents facing jail for corruption. In fact, we have had three since last Friday.
In South Korea, former president Park Geun-hye was sentenced to 24 years in prison and fined $17 million on Friday for bribery, extortion, abuse of power and other offences. She is guilty as charged, but she is also a victim.
On Saturday, former South African president Jacob Zuma appeared in a Durban court to face corruption charges over a $2.5 billion arms deal soon after his own party forced him to resign a year before his term ended.
Since Zuma's former financial adviser has already served jail time on identical charges, his chances of a happy retirement seem rather slim.
And on Sunday, former Brazilian president Luiz Inácio Lula da Silva, universally known as "Lula", began serving a 12-year jail term for corruption. However, he's probably not guilty of anything that would justify his imprisonment.
That's three gone or going in one weekend, and there are others in the queue – like former French president Nicolas Sarkozy, who faces charges that the late Libyan dictator Muammar Gaddafi illegally funded his 2007 presidential campaign.
Running a country is clearly a high-risk job, and the people who get the job tend to be risk-takers. Not all of them are rich, and they are exposed to many temptations.
Nevertheless, not all cases of corruption are about simple self-enrichment.
Ex-president Park's was not, although she collected at least $35 million in bribes from major Korean companies, including Samsung and the giant retailer Lotte. But Park Geun-hye was doing it all at the behest of her confidante, Choi Soon-sil, the daughter of a preacher and cult leader who won the trust of Park's father more than 40 years ago.
The ex-president's father, Park Chung-hee, ruled South Korea as a military dictator in the 1970s. When Park Geun-hye's parents were both assassinated, the orphaned girl was befriended by the preacher's daughter, Choi Soon-sil, who established a comparable control over her.
In 2013 Park Geun-hye was elected to the presidency, but Choi Soon-sil's influence never weakened.
The bribes that Park received while in office almost all went to foundations controlled by Choi. Both women have gone to jail, and both deserved to, but Park was as much a victim as a villain.
Jacob Zuma's is a simpler story. He was a major figure in the African National Congress during the decades of struggle against apartheid, first in prison on Robben Island and then in exile as the ANC's head of military intelligence (his former chief of staff in that job once described him to me as a "military genius").
But Zuma had no money, and when he got political power in post-apartheid South Africa he set about to remedy that problem. There has never been any real doubt that he benefited enormously from the arms purchase deal, and he was forced to resign the deputy presidency in 2005 – but after he was elected as leader of the ANC in 2007 he managed to get the charges dropped.
By 2009 he was the president of South Africa, and for the next nine years the charges remained in abeyance. When he was forced out of office two months ago for further brazen acts of corruption and for general economic mismanagement of the country, the charges were resurrected almost instantly, and now he faces a world of woe. About time too, many would say.
And Lula? There probably was no crime in the first place. Brazil is going through an enormous corruption scandal and more than half the members of Congress face charges, but so long as they control Congress and the presidency they can probably stave them off.
An election is due in October, however, and Lula would probably win it – if he were not in prison.
The crime he is charged with is petty by Brazilian standards: accepting free renovation work when his wife moved to a bigger holiday apartment in the seaside town of Guaraju.
His judgement may have been clouded at the time, because he was fighting cancer, but in any case he was no longer in office and unable to do any political favours in return. He denies the whole thing, but at worst it was foolish to accept the help, not corrupt.
Lula still lives in the industrial city of Sao Bernardo do Campo, 20 kilometres from Sao Paulo, in a modest house within walking distance of the steelworkers union headquarters where I first interviewed him almost 40 years ago. He is an honest man of simple tastes, but at the moment he is sitting in jail.
He still has an appeal working its way up through the courts, but it's unlikely to set him free. The real reason he is in jail is to keep him from contesting the election, so there he will stay.
The rule of law is an excellent thing, but no system devised by human beings is invulnerable to manipulation by other human beings.
Gwynne Dyer is an independent journalist whose articles are published in 45 countries.