The man who abducted, raped and murdered Wellington jogger Margaret-Lynne Baxter will now serve 17 years in jail before he is eligible for parole.

The Court of Appeal in Wellington ruled yesterday that the original 15-year non-parole term imposed on Dartelle Alder was "manifestly inadequate" and ordered him to serve a further two years.

Justices Peter Blanchard, Andrew Tipping and John McGrath said they did not consider the non-parole period could realistically have been less than 17 years.

"The lowest tenable starting point, in our view, is one of 18 years and the most that can be allowed for the mitigating matters [mainly Alder's guilty pleas] is one year."

Alder's sentence, imposed in the High Court at Napier in December, was appealed by the Crown, which sought a minimum stretch of 20 years.

Alder, 23, used his car to run down Ms Baxter, 38, as she jogged near the Hastings suburb of Flaxmere on January 21 last year.

Alder put her in his car and drove to a house where he raped her, stabbed her more than 30 times and finally killed her by smashing a terracotta tile on her head.

The Appeal Court said Alder killed Ms Baxter to silence her in an attempt to escape responsibility for "conduct of the most heinous kind".

Crown counsel Simon France said last week that the Crown's only complaint about Alder's High Court trial covered the ultimate outcome.

He said Justice Warwick Gendall's starting point of 17 years for a prison term had been too low and his two-year discount for guilty pleas had been too great.

Defence lawyer David Madsen said the 15-year non-parole period was adequate given Alder's guilty plea to the murder, his absence of previous convictions and his good record in the community.