Mr Harnett, 58, a volunteer firefighter from Coromandel, died when the motorbike he was riding collided with Walker's car at the intersection of Marsden Point Road and State Highway 1 at Ruakaka, on April 15, last year.
He was one of three motorcyclists killed in crashes in Northland that month.
Discussing with the judge whether a presentence report was necessary, counsel Sumudu Thode said given Walker's age, health conditions, and lack of previous convictions, an electronically-monitored sentence was unlikely – as was community work.
Her submissions at sentencing would be in support of reparation for emotional harm, a driver disqualification, and possibly also a fine, Thode said.