A driver accused of fatally striking an Adelaide toddler before leaving the accident scene has told a District Court jury he thought he had hit a ball.

Key points: Mr Bullock's wife Donna called emergency services after being told about the crash

Mr Bullock's wife Donna called emergency services after being told about the crash Zayne was struck as he played outside his Dover Gardens home in 2017

Zayne was struck as he played outside his Dover Gardens home in 2017 Mr Bullock has pleaded not guilty to dangerous driving causing death in the District Court

Giving evidence in his defence today, Michael Bullock told the court he was driving along a Dover Gardens street at about 35 kilometres per hour when he came up to a tree.

He said a little girl ran out from behind the tree.

"I was about two metres from her. I swerved to miss her, I heard a noise at the front of my car," he said.

"Then I felt something go under my rear wheels. I thought it was a ball. I don't know."

He said he thought the girl had run out to chase the ball.

"I didn't know what it was. I didn't see anything," he told the jury.

"I stopped the car. I saw a child lying on the ground. I panicked.

"I didn't know what to do so I went home to phone the police or someone to get help."

He said the crash happened 80 metres from his home.

Accused denies driving dangerously

Mr Bullock has denied he was driving dangerously when he struck and killed two-year-old Zayne Colson in February 2017.

His wife, Donna Bullock, also gave evidence today, saying she called emergency services "within seconds" of her husband telling her about the crash.

The jury was played a recording of the call, in which Mr Bullock can be heard in the background saying "I just ran over a kid".

The operator asked Mrs Bullock if the child was conscious, who then relayed the question to Mr Bullock who responded "I don't know, I don't think so".

Mr Bullock can also be heard saying "I didn't stop — it wasn't safe".

She was asked if she had enquired with authorities about the toddler's condition. Mrs Bullock replied: "I didn't".

"Michael was, pretty, in a mess. I was concerned about everything," she said.

Mr Bullock has pleaded not guilty to a number of offences, including aggravated driving without due care, not providing assistance and leaving an accident scene.

Last week, prosecutor Rachael Gray SC said in her opening address to the jury that Mr Bullock struck the toddler almost in the middle of Branksome Terrace and then kept driving.

"He was dragged underneath the car for a few metres and was left lying in the road," Ms Gray said.

The jury was told Mr Bullock did not stop because he feared for his safety.

But Ms Gray said there was not anything that made it unsafe for him to stop, and the only people nearby at the time of the crash were Zayne's sisters — aged five and seven.

Paramedics unsuccessfully tried to resuscitate Zayne but he remained unconscious and died at 9:00pm that day.

The trial before Judge Paul Cuthbertson and a jury of 12 continues.