Miroslav Marcek acknowledged that he shot dead Jan Kuciak and Martina Kusnirova in February 2018. Three other defendants, including the businessman accused of being the mastermind of the slayings, pleaded not guilty to murder.
Prosecutors at the court in the town of Pezinok, north of the capital Bratislava claim a total of 70,000 euros ($77,640) was paid. The suspected mastermind, Marian Kocner, is a businessman who had allegedly threatened the journalist following publication of a story about him.
The 27-year-old Kuciak was shot in the chest and Kusnirova was shot in the head at their home in the town of Velka Maca, east of Bratislava, on Feb. 21, 2018. The killings triggered major street protests and a political crisis that led to the previous government's collapse. Kuciak had been also investigating possible government corruption.
The four defendants face potential prison sentences of 25 years to life. A fifth suspect made an agreement to cooperate with prosecutors in exchange for a lower sentence and received a 15-year prison term on Dec 30.
It is not clear when a verdict might be issued.