Jurors have started hearing evidence against a father and son charged with murdering a 21-year-old man in 2017.

Kurt Grech, known as in-Nemes, and his father Joseph are pleading not guilty to the murder of Brandon Pace on April 2 in Giovanni Barbara Street. They are being charged with wilful homicide, unlawful possession of knives, breaching public peace and good order and threatening the victim's mother and the mother of Grech's son.

Grech is also being charged with grievously injuring the mother of his son with a knife. His father Joseph is also charged with having threatened the victim's sister with a knife during the fight.

The prosecution said that at about 8pm on April 2 the police were informed of a murder in Ħamrun. When they arrived on the scene, police were told that the victim was found in a pool of blood in the common area of an apartment block.

Investigations found that Pace was at his girlfriend's home when Kurt Grech arrived as started insulting the girlfriend, with whom he has a son.

Grech told police that he went there because the girlfriend called his mother and insulted her over an issue involving their son. He took two knives with him in case Pace was there.

Pace confronted Kurt and Kurt's parents arrived in a separate car.

A fight erupted involving the girlfriend, Pace, Kurt and his parents. Witnesses told police that, at one point, they saw Pace fall to the ground and Kurt jumped on him. Both had knives on them in the moment.

According to Pace's mother, when her son tried to walk into the apartment block, Joseph stabbed him in the back. Kurt Grech had to be taken to hospital for treatment after suffering injuries to his side.

The father and son were charged in court days after the incident.

Lawyers Roberto Montalto, Katheleen Grima and Edward Gatt are defence counsel. Lawyers Rachel Tua and Ishmael Psaila are representing the victim's family. Attorney General lawyers Kevin Valletta and Kaylie Bonett are prosecuting.