54 people are charged with involvement in the murder of Catalán and her colleagues.
The trial has been held in a military court in Kananga.
On Saturday, it was announced that Colonel Jean de Dieu Mambweni, who had previously been accused of lying about the murder during a trial, was sentenced to 10 years in prison for misconduct.
The trial shows that he has not followed instructions and failed to help people in danger, writes the Congolese newspaper Actualité.
More rulings are expected in the future.
Catalán was abducted and murdered along with his American colleague Michael Sharp and local aide Betu Shintela when they were on a mission in the province of Kasaï Central in March 2017. A few weeks later, the Swede and the two other murder victims were found buried in the area.
The militia Kamuina Nsapu is believed to have been behind the attack on the Swede and her colleagues.
Catalán worked as an expert for a UN committee directly under the UN Security Council with the task of monitoring sanctions against the country and investigating suspected massacres in the Kasair region, where there has been an armed conflict between Kamuina Nsapu and government forces.
The conflict that was going on in the region at that time claimed thousands of lives and many people were forced to flee their homes.