Politicians tend to lie. It is a common belief that one cannot become a successful politician without telling lies, which makes politics one of the professions that the public trusts least.

The Sung Woan-jong scandal that has been pounding the political community confirms this public belief.

Many of those whose names have come up so far had denied Sung’s claims that they were close to the late tycoon and received illicit money from him. One after another, they changed their words as evidence and testimonies to the contrary emerged.

Take Prime Minister Lee Wan-koo for example. Lee’s name was in a memo Sung left in his pocket when he committed suicide, which listed eight politicians ― six of them had amounts of money listed beside their names.

At that time, Lee said he was not so close to the late tycoon, even though they were in the same party and from the same central Chungcheong region. Then he changed his words after a memo containing Sung’s daily schedules showed that he met the tycoon 23 times in 20 months ― from August 2013 to last month.

Lee said that being a floor leader, he had to meet lawmakers ― Sung was a lawmaker of the ruling party ― frequently, but still denied he had any special relationship with Sung.

Then came Sung’s comments ― released by a newspaper posthumously ― that he gave 30 million to Lee to help his campaign for the parliamentary by-elections held on April 24, 2013. Sung pinpointed April 4 as the day he personally visited Lee’s campaign office to deliver the money.

At first, Lee strongly denied this allegation too, saying that there were many people in the office and that the circumstances did not allow him to meet Sung personally.

Lee changed his words again after testimonies from Sung’s aides and none other than his own driver supported the claim. Lee then said that there were a lot of things going on during the hectic campaign days and that he could not remember everything.

Hong Moon-jong, a ruling party lawmaker, was mentioned by Sung both in the memo found in his pocket and a telephone conversation between Sung and a newspaper editor. Denying Sung’s claim that he was given 200 million in 2012 in election funds for President Park Geun-hye, Hong said that he knew Sung as no more than an acquaintance or a fellow lawmaker and that they never met personally.

According to the memo on Sung’s schedule, Hong met Sung 18 times in 20 months.

Kim Ki-choon, Park’s former chief of staff, had flatly denied Sung’s claim that he received $100,000 in 2006 shortly before he visited Germany and Belgium to accompany Park.

Kim said that the allegation was “absurd and groundless” and that Sung wrote a “fiction,” adding that he never met Sung while he was in the Blue House. The memo on Sung’s schedules showed otherwise, and Kim admitted meeting Sung over dinner in November 2013.

Things like these not only consolidate public suspicion about the politicians implicated in the case but also worse the already strong public distrust of politicians as a whole.

Prosecutors said that they have seized tens of diaries, pocketbooks and cell phones from Sung’s aides and they have begun summoning them for questioning.

So we may well see more names and new suspicions and allegations ― for which many will first resort to their habit of lying. This imposes heavy responsibility on the prosecution to shed light on lies and punish liars.