A woman on trial for murder was heard yelling she was "going to find the boys and kill them" before she got into her car and ploughed into a group of teenagers in Canning Vale, fatally injuring one of them, the WA Supreme Court has been told.

Key points: A fight between two groups of school students kicked off a deadly set of events

A fight between two groups of school students kicked off a deadly set of events Aya Hishmeh's brother and sister were injured during the fight

Aya Hishmeh's brother and sister were injured during the fight She admits hitting a group of boys in her car, but denies a charge of murder

Aya Hishmeh, 22, is alleged to have deliberately run down the five teenagers at high speed on Eucalyptus Boulevard on the afternoon of December 7, 2017, in what prosecutors have described as "an act of vengeance".

Jacob Cummins, 17, died in the incident and Ms Hishemh is is now on trial accused of his murder.

She has also been charged with attempting to kill Robert Bell, Anwre Ige and Augustine Janga, who were seriously injured.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 49 seconds 49 s Helicopter footage shows the aftermath at the scene.

Ms Hishmeh has admitted driving dangerously but maintained she had only wanted to warn the teenagers to stay away from her family and had not meant to kill or harm anyone.

Her lawyer, Anthony Elliott, said an expert would testify that Ms Hishmeh's car was going too fast and, even if maximum braking was applied, she would not have been able to stop before she hit the teenagers.

Park fight set off deadly chain of events

The court has heard the incident happened after Ms Hishmeh heard her brother had been set upon during a fight in a park between school students. She also saw her sister had been slashed on the arm.

It was alleged she then got into her car to track down the perpetrators. When she saw the group of boys at a bus stop, she accelerated towards them at a speed of about 78 kilometres per hour.

Police examine the car the hit that teenagers, killing one. ( ABC News: Andrew O'Connor )

CCTV footage has been played to the court showing the moment the boys were hit by the car, which resulted in one of them flying through the air and another ending up lodged in the windscreen of the car.

Three teenagers who were in the car park of a nearby fast food outlet testifed they heard Ms Hishmeh yell she was "going to kill them" after she saw her sister had a slash wound to the arm.

Jacob Cummins died after he and a group of teenagers were hit by a car allegedly driven by Aya Hishmeh. ( Supplied: Family )

The witnesses said Ms Hishmeh appeared "very angry" and was pacing up and down.

One of them said she heard Ms Hishmeh say "multiple times" she "was going to kill them and their family", while another witness said she heard Ms Hishmeh say she "was going to find the boys and then she was going to kill them … kill everyone".

Witnesses say they heard Aya Hishmeh say she wanted to kill the boys before the incident. ( Instagram: @ayahishmeh )

Another witness said she saw Ms Hishmeh make a phone call before a man arrived in a red car, and after a conversation Ms Hishmeh got into the driver's seat and left the car park.

The trial is expected to run for four weeks.