Vic man jailed for death of dog walker

A motorist who killed a man walking his dog while driving erratically under the influence of heroin, east of Melbourne, has been jailed for at least five years.

Dillon Buckley, 27, caused the death of 58-year-old Guy Williams, seriously injured his partner Mardi Trease, 68, and injured their dog Jamie when he hit them from behind at Wandin East on December 9.

He had taken heroin 15 minutes earlier.

Witnesses variously observed Buckley driving erratically, cutting a corner, driving at high speed on gravel, driving half-off a bitumen road and appearing to travel sideways at times.

After crashing into his victims, Buckely slammed into a tree and his car flipped onto its roof.

He was seen trying to push the vehicle back onto its wheels and appeared to be alcohol-affected.

The County Court heard on Tuesday Buckley told a witness "I don't care" when informed he'd hit two people and a dog.

He then fell asleep on the grass.

Mr Williams died at the scene, while Ms Trease was airlifted to hospital suffering two broken legs, a broken pelvis, a broken hand and humerus, a broken cheekbone and nose and a brain injury.

The keen horserider and bushwalker hadn't ridden or gone hiking since the accident and was unable to work in her job as a vet surgeon for more than six months.

Judge Martine Marich accepted Buckley, who had previously pleaded guilty to culpable driving and negligently causing serious injury, was now remorseful for his "appalling" offending and its "devastating consequences".

He was jailed for seven-and-a-half years with a minimum of five years before being eligible for parole.

Outside court, Ms Trease told reporters she thought the sentence was very reasonable.

"(Guy) was a lovely man who liked to be by himself or with me or his family but he just loved the bush and the birds," she said.

She hoped Buckley would be rehabilitated into society after prison.

"I'm just hoping and I'm sure he will, that he'll get better and that he won't take drugs anymore and it sounds as though he's got support," Ms Trease said.

"Hopefully when he gets out of jail, he'll lead a good life."