A magistrate said in June that Sharon Mortlock acted in a ''callous and inhumane'' way when she drove away from Carr Crescent, Wanniassa in the early hours of August 22 last year, leaving Luke Stefani dying in the street.

The Eden woman pleaded guilty in the ACT Magistrates Court to negligent driving causing death.

She was given 15 months in jail that was to be wholly suspended after she had served nine months of periodic detention. But in papers filed to the ACT Supreme Court, Mortlock's lawyers say the sentence handed to their client was ''manifestly excessive''.

Sentencing Mortlock in June this year, Magistrate Maria Doogan said the offender, who recorded a blood-alcohol reading nearly four times the legal limit a few hours after the incident, had shown no remorse over the death of Mr Stefani.

''She appears to me to lack any genuine remorse and has made no constructive or sufficient effort to address her obvious alcohol addiction,'' Ms Doogan said.

''She is in most respects the author of her own misfortune.''

Ms Doogan also noted that Mortlock had an extensive criminal history.

The 41-year-old has convictions going back 25 years for drink-driving, assault, assault occasioning actual bodily harm, theft and failing to comply with court orders.

The magistrate said Mortlock had offered no excuse for fleeing the scene after she had driven for more than 100m with her victim clinging to the bonnet of the car and then slammed on the brakes, throwing Mr Stefani fatally on to the road.

''There is no evidence, nor any explanation before the court as to why the defendant fled the scene,'' Ms Doogan said.

''This was a callous and inhumane response to the plight of another human being, by the defendant.

''In reality she left Mr Stefani lying on the road where he died shortly after...''

Mortlock's lawyers will go before the Supreme Court today arguing the sentence was manifestly excessive.

Their appeal papers say the magistrate erred both in her determination of the seriousness of Mortlock's criminality and in the factual basis of the case.

It is also claimed Mortlock did not get enough of a discounted sentence for pleading guilty and that the magistrate was mistaken in finding the offender's criminal history aggravated the seriousness of her crime.

They want Mortlock's weekend jail sentence set aside and for her to be re-sentenced.

The Supreme Court is due to hear the case this morning.