The court ruling that found former President Lee Myung-bak guilty of seven charges manifests the assortment of problems ingrained in Korean politics.

Most of all, the lower court’s ruling that sentenced Lee to 15 years in jail -- he was also ordered to pay 13 billion won ($11.5 million) in fines and forfeit 8.2 billion won -- is further evidence the Korean presidency is highly vulnerable to corruption and abuses of power.

The 77-year-old Lee, who was in office from 2008-2013, is the fourth president to be convicted of corruption charges. Former Army generals-turned-presidents Chun Doo-hwan and Roh Tae-woo were found guilty of pocketing huge sums of money from tycoons. They were also charged with munity and treason for masterminding a coup that put them in power.

Lee’s immediate successor, Park Geun-hye, was impeached for her role in the corruption and influence-peddling scandal involving her civilian confidante Choi Soon-sil. An appeals court sentenced Park to 25 years of prison in August.

Unlike Park, who was charged mainly with aiding Choi in extorting money from conglomerates, major charges against Lee were related to an auto parts company run by his family. Lee insisted the company, DAS, was owned by his brother and brother-in-law, but the court ruled Lee is the de facto owner of the company.

The court said testimonies from Lee’s former aides and incumbent and former executives and employees of the company “were sufficient” to believe Lee is owner of the company.

The court found Lee guilty of amassing a slush fund amounting to 2.46 billion won through DAS, as well as embezzlement of the fund. This ruling, if upheld by the appeals court and Supreme Court, would put an end to the dispute over the ownership of the company that has heated up Korean politics from time to time since 2007 when Lee ran for president.

The court ruling showed that after becoming president, Lee exploited his power to help DAS. In one prime case, Lee was behind the decision in 2009 of Samsung Electronics to pay the legal fees for DAS when it was embroiled in a lawsuit in the US.

The court saw the 5.9 billion-won legal fee as a bribe given in return for presidential special amnesty granted to Samsung Chairman Lee Kun-hee, who had been convicted of tax evasion charges.

Elsewhere, Lee was found guilty of receiving about 2.4 billion won in bribes from a financial company chairman, a former intelligence agency chief and a former lawmaker.

Lee’s conviction, which came about two months after the appellate court ruling on Park, demonstrates the backwardness of Korean presidential politics. Again, the biggest problem is that Korean presidents -- accorded strong power under the Constitution -- are prone to corruption, influence-peddling and abuses of power.

Lee’s case should be another reminder that political parties should accelerate their work to revise the supreme law in a way to curtail the power of the president.

Both Lee and Park, now kept in separate detention houses, claim they did nothing wrong, arguing they are victims of political vendetta. They have been boycotting their trials and made the court’s decision to allow the live broadcast of the sentencing meaningless by staying out of the courthouse.

True, there are some grounds to their allegations. Korean politics has a bad tradition in which the government in power mobilizes law enforcement authorities and other powerful agencies to investigate past governments.

Nevertheless, the charges against Lee and Park are so grave that the two former leaders’ arguments that they are completely innocent do not make sense. Instead of making such arguments they require sincere soul searching, as well as apologies to those who got them elected.