Mitchell Darkes, 28, of Bacchus Marsh, attended the Cobden BP Roadhouse service station on November 23 last year about 8.15am, produced a large knife and demanded cash.

He pleaded guilty to armed robbery in Melbourne County Court on Wednesday.

The court heard Darkes was the front passenger in a green utility allegedly driven by Camperdown's Damien Searle, 35.

Mr Searle allegedly parked the vehicle behind a motel located about 65 metres from the Cobden roadhouse.

Darkes exited the vehicle, walked into the service station and asked the 22-year-old female employee where a bathroom was.

He then waited in the toilet for seven minutes for all customers to leave the building.

Darkes approached the female victim at 8.23am and demanded cash while brandishing a large knife.

The victim froze and ran into the kitchen where two other females, aged 25 and 54, were located.

Darkes jumped the counter, entered the kitchen and again made demands for money.

READ MORE:

The three victims left the kitchen and the 54-year-old victim handed the man $565 cash.

Darkes ran back to the green utility which fled the scene at high speed.

Later that morning Darkes was located at a property in Camperdown's Gunner Street.

He was found lying on the bottom bunk of a bed.

A large knife was seized and Darkes was arrested.

The court heard Mr Searle was arrested at the Royal Alfred Hospital on December 3 after he was seriously injured in an unrelated motorbike accident some days earlier.

Darkes denied knowledge of the armed robbery, stating he'd never been to Cobden.

At the time of the offending he was on bail charged with committing a separate armed robbery in the Frankston area.

On Wednesday the court heard Darkes was previously remanded for the first robbery and had served 525 days in custody, some of which was spent in a management unit due to previous gang activity.

A psychologist told the court Darkes suffered personality, antisocial and stimulant-use disorders.

He said the disorders stemmed from Darkes suffering childhood instability, emotional neglect and witnessing violence in the home.

The psychologist said Darkes started using drugs at 13 which impacted on his future capacity to "think through consequences, think rationally and access a stable sense of self".

He said it also led to impulsivity and self-sabotaging behaviours.

Darkes' lawyer told the court his client had spent a large proportion of his life in prison and would benefit from a drug treatment order, which he said was expected to be introduced to the County Court from May 31.

A drug treatment order combines a term of imprisonment with drug treatment but with the term of imprisonment suspended.

The court imposes a sentence of up to two years' imprisonment but defers the term of imprisonment while the offender undergoes treatment and supervision.

Currently the orders can only be ordered by a specialised division of certain magistrates' courts and cannot be given to offenders who have committed sexual or violent crimes.

Judge Duncan Allen said Darkes was facing a "significant" jail sentence.

"That is unavoidable given his (criminal) history and the aggravated circumstances of the offending," he said.

"(Darkes) was already on bail for an armed robbery committed in similar circumstances. A significant (jail) sentence is unavoidable."

But the judge said Darkes was still aged 28 and "ought not be written off just yet".

"He ought to be given the opportunity of rehabilitation," he said.

The plea hearing will continue on June 11.

He remains on remand.

Our journalists work hard to provide local, up-to-date news to the community. This is how you can access our trusted content