A court in Slovakia has sentenced a former soldier to 23 years in prison for the murder of the investigative journalist Ján Kuciak and his fiancee, Martina Kušnírová, in February 2018.

The double murder of the recently engaged couple, both of whom were 27 at the time, shocked Slovakia and led to protests that eventually led to the resignation of the prime minister.

On Monday, a court in Pezinok, north of Bratislava, handed down the sentence to 37-year-old Miroslav Marček. He was also convicted of carrying out an unrelated hit on a businessman in 2016. The alleged mastermind of the murder, a businessman who had previously threatened Kuciak, will stand trial in a separate court case.

“It was cold-blooded and malicious. The victims did not have a chance to defend themselves,” said the presiding judge, Ruzena Szabova, handing down the verdict to Marček. She said his confession and eventual cooperation with authorities had been a mitigating circumstance. Marček can appeal to Slovakia’s supreme court over the verdict.

Kuciak was a young and well-liked reporter specialising in data journalism, who had reported on corruption and links between the crime world and official figures for the Slovak news outlet Aktuality.sk. At the time of his death, he was midway through an investigation about links between Italian mafia groups and the Slovak political system.

The businessman Marián Kočner is accused of organising and paying for the murder. Three other people are also charged with aiding the murder. Last month, Slovak police said they had arrested 18 people, including 13 judges, who are accused of attempting to obstruct the investigation into the murders.

Kočner has admitted carrying an illegal firearm but denies murder. Kuciak had written about Kočner and even been threatened by him, but few believed his life was in danger, and the murders shocked the country. The killings sparked large-scale protests, which led to the resignation of long-standing prime minister Robert Fico a month later. Then, last year, the liberal former civil society activist Zuzana Čaputová won the presidency after promising a gentler and kinder politics.

Fico’s Smer party continued to be the governing party until two months ago, when it was ousted by a coalition of four other parties, after a general election campaign in which rule of law and the legacy of the Kuciak murder played a large part.

Kočner’s trial is due to start later this month.