Key Points:

A Christchurch motorist has admitted killing the mother of the city's ACT parliamentary candidate Aaron Keown.

Arcanie Vincent Optetaia Matagi, a printer, pleaded guilty in Christchurch District Court today to dangerous driving causing the death of Laureen Helen Reilly, but the Crown was given three weeks to decide whether to proceed with a manslaughter charge instead.

Mrs Reilly's death in a crash on Christchurch's Main North Road on May 6, led to Mr Keown deciding to stand for Parliament to campaign for harsher sentences for criminals.

Police say Matagi was overtaken by another driver travelling at 120km/h.

Matagi then overtook that car but lost control at the end of the manoeuvre, spun across the road and crashed into another car killing Mrs Reilly, and seriously injuring another person.

Judge David Holderness remanded Matagi, who had no previous convictions, on bail to November 25 for a pre-sentence report, reparation report, and a report on his suitability for home detention.

The judge said the granting of bail was not an indication of a non-custodial sentence being imposed.

The Crown must decide by October 8 whether to go ahead with the manslaughter charge.

Brad Jordan Nicholls, whose car was overtaken by Matagi, has pleaded guilty to dangerous driving.

Police say his car crashed into the back of Matagi's vehicle during the pile-up.

Defence counsel Clayton Williams said no drugs or alcohol had been involved. Nicholls did not know Matagi and denied they were racing.

Police dispute that, and a disputed facts hearing to decide whether the cars were racing, is set for September 24.