Tradie killer denies stabbing was murder

After a nice dinner tradie Cameron Smith and his friend Natasha Stroumos planned to watch the sunset from a Melbourne beach.

But Mr Smith was killed before they made it.

Prosecutors say he was murdered, but his killer Jack Ledlin denies he intended to kill the man he stabbed directly in the heart.

"Because you cause the death of someone doesn't mean you have a murderous intent," Ledlin's barrister Michael McGrath told a Victorian Supreme Court trial on Wednesday afternoon.

Ledlin, now 21, has pleaded guilty to manslaughter, but is being tried for murder on the basis that he intended to cause really serious injury to 26-year-old Mr Smith.

Neither man had met the other before the evening of November 25, 2020 but their girlfriends had a brief dispute at a house party the previous New Year's Eve.

That formed a back story to the incident, which was not completely random, prosecutor Jane Warren said.

After their dinner, Ms Stroumos and Mr Smith - who broke up months earlier but remained good friends - went back to their car at Seaford Train Station to drop off some leftovers.

On the way they passed Ledlin and his girlfriend Scarlett Taylor, who called out that Ms Stroumos was a "slut" and "fat bitch".

Ledlin yelled out "dog" and "keep f***ing walking".

Neither Mr Smith nor Ms Stroumos reacted to the abuse. On their way back from the car they ran into Ledlin, Ms Taylor and two other men.

Ms Stroumos will give evidence that she saw a man, not Ledlin, punch Mr Smith to the face, Ms Warren told the jury.

Mr Smith asked "do you want to go" and struck the man back before a fight broke out, she said.

Several people witnessed the fight, including one man who filmed it.

The moment of impact is obscured in the footage, but Ms Warren alleged it shows Ledlin raised his arm, swing it toward Mr Smith and strike him in the chest with a sharp bladed object.

The video, played in court on Wednesday, showed Ledlin holding a sharp object.

Mr Smith took a few steps backward before collapsing. He was immediately unresponsive and died at the scene.

An autopsy revealed the sharp object went straight through his heart and severed the coronary artery, causing significant blood loss.

The other two men in the group ran toward Mr Smith and kicked him in the head, before running from the scene with Ledlin and Ms Taylor.

Mr McGrath said it was only through coming to the aid of his friend that he became involved.

Much of the evidence is not in dispute but Ledlin didn't intend to strike Mr Smith or to cause him really serious injury, he said.

Evidence in the trial is only expected to take three days before closing addresses early next week.

Ms Stroumos will be the first witness.