A pre-trial hearing ahead of a long-awaited trial of Slovak businessman Marian Kocner, suspected of ordering the 2018 assassination of investigative journalist Jan Kuciak, opens Thursday, the Special Criminal Court said.

Kuciak had been investigating business activities of property developer Marian Kocner, when he and fiancee Martina Kusnirova were gunned down at home near the capital Bratislava in a gangland-style hit in February 2018.

The double homicide triggered mass anti-government protests that forced then-premier Robert Fico to resign and paved the way for the election of liberal anti-corruption activist Zuzana Caputova as president in March.

Prosecutors have charged Kocner with ordering Kuciak's assassination.

Slovak entrepreneur Marian Kocner, seen in February 2018, is accused of ordering the murder of investigative journalist Jan Kuciak, whose killing triggered mass protests that toppled the then prime minister
Slovak entrepreneur Marian Kocner, seen in February 2018, is accused of ordering the murder of investigative journalist Jan Kuciak, whose killing triggered mass protests that toppled the then prime minister AFP / TOMAS BENEDIKOVIC

"A senate headed by judge Ruzena Sabova will carry out preliminary proceedings concerning the charges in the case of the murders of journalist Jan Kuciak and his girlfriend Martina Kusnirova on Thursday," Wednesday's court statement said.

Thursday's proceedings will involve an examination of the charges and the legality of the evidence, the local TASR newswire said. If serious procedural errors are discovered, the court can refer the charges back to the prosecutor who pressed them, under the Slovak penal code.

If no serious procedural errors are determined, the court will set the date for launching the main proceedings.

Prosecutors have charged five people over the double murder, including Kocner and his one-time interpreter Alena Zs. One of the suspects, Zoltan A, who acted as intermediary, has made a plea bargain, pending court approval.

The double killing of Kuciak and his fiancee Martina Kusnirova plunged the country into crisis and sparked mass demonstrations
The double killing of Kuciak and his fiancee Martina Kusnirova plunged the country into crisis and sparked mass demonstrations AFP / VLADIMIR SIMICEK

In the meantime, the 93-page indictment leaked out to local media.

The document says that Kocner failed to find "any dirt" on the journalist to discredit him, which led the accused "to decide to get rid of Jan Kuciak physically and thus prevent further disclosure of his (Kocner's) activities".

"If convicted, the accused face a minimum 25-years to life imprisonment," Jana Tokolyova, a spokeswoman for the special prosecutor's office,told AFP earlier.

Investigators have revealed that Kocner exchanged thousands of messages with senior government officials from the ruling Smer-SD party.

Former prime minister and Smer chairman Robert Fico blamed the opposition and the media for linking his party to Kocner, telling reporters that their coverage against the party was "turning into a kind of jihad."

Fico remains the party leader and is widely seen as still pulling the strings.

Bratislava-based analyst Pavol Babos told AFP that "Robert Fico is definitely losing coalition potential" in the lead-up to a February general election.

"I cannot imagine political parties entering into a coalition with Smer-SD," Babos said.

Support for Smer-SD has dropped to an historic low of around 20 rpercent, but it is still poised to win the poll.