Ljubljana - The story of Ivan Kramberger, a man of the people who ran for president in 1990 in the first multi-party elections in Slovenia, has been put on film that will premiere tonight at the Cankarjev Dom arts centre in Ljubljana. Although a man was found guilty of his killing, Kramberger's 1992 death is for many still a mystery.

The feature-length documentary Beli Bojevnik v Črni Obleki (White Warrior in Black Suit) tells a story about the role Kramberger (1936-1992) played in Slovenia's independence efforts.

At the same time, it shows his son Ivan Kramberger Jr. researching his father's independence role, and death in 1992, for his master's degree before the camera.

It is thus also "a story about the son's 30-year search for the truth about his father", Cankarjev Dom said, adding Kramberger "died in the first assassination in independent Slovenia".

Kramberger announced he would stand in the 1992 general election, but was shot on 7 June in the village of Jurovski Dol before the election campaign even started.

The shooter, who was under the influence of alcohol, was sentenced to prison for killing Krambeger, yet the motive for the murder has never been fully clarified.

Assassination speculations are fuelled by the fact that he and his party, if elected, might have been a strong political player at a key period of Slovenia's transition.

Kramberger, a man of humble background who started as a chimney sweeper, worked in Germany between 1963 and the early 1980s, during which time he filed patents for a number of improvements to dialysis devices. Upon returning to Slovenia, he ran a restaurant at his new home in the town of Negova, where he lived with his family.

In the late 1980s and early 1990s, he would drive cars he had made himself, travelling around Slovenia to hold speeches that drew sizeable audiences as he spoke about common people's hardships while selling his books with a monkey on his shoulder.

With voter support, he stood in the presidential election to win 18.5% of the vote placing third among four candidates, behind Milan Kučan (44.4%) and Jože Pučnik (26.6%).

In the documentary, his son interviews independence figures, ministers in the independence government (1990-1992), historians, journalists, his father's aides and family members, while he also watches a vast body of archived material.

Appearing in the documentary are for instance PM Janez Janša, who served as defence minster at the time, ex-President Kučan, then PM Lojze Peterle and then Foreign Minister Dimitrij Rupel.

The film was directed by award-wining film director Maja Weiss. She wrote the screenplay together with Kramberger's son, who was six when his father was killed.

The film is a co-production of Weiss's Bela Film and public broadcaster RTV Slovenija, and received public co-funding as part of the 30th anniversary of Slovenian independence celebrations. Another screening is scheduled for 20 December in Maribor.