The man who ran down, raped and killed Margaret Baxter is being held at a medium security prison - to the disgust of guards and tougher sentencing advocates.

It was confirmed yesterday that Dartelle Alder, aged 24, of Hastings, was an inmate at Hawkes Bay Regional Prison at Mangaroa, which the Corrections Department classified as a medium security facility.

Last month, Justice Warwick Gendall sentenced Alder to life imprisonment with no parole for 15 years for the brutal rape, torture and murder of Miss Baxter a year ago. Justice Gendall described the crime as "cruel and unspeakable".

Alder was convicted of deliberately using his car to run down the Wellington woman as she returned alone from a summer morning's jog with her boyfriend in the countryside near Hastings during Wellington Anniversary weekend.

A department spokesman said inmates were assessed individually based on factors such as the seriousness of the offence, the length of sentence, history of escapes and whether further charges were pending.

It is understood that Alder, who is a first-time offender, has been assessed as suitable to be kept at Mangaroa.

Brian Davies, national organiser of the prison officers' union, the Corrections Association, said the classification was not high enough, given the severity of Alder's crimes and public expectation that convicted murderers were kept in maximum security prisons.

"Clearly, anyone who has raped and murdered a person at the drop of a hat is totally unpredictable and should have the highest security rating possible," Mr Davies said.

Sensible Sentencing Trust chairman Garth McVicar said Alder's security status showed little consideration for Miss Baxter's family.

"I understand that he has had no previous offence, but he has committed one of the most horrendous crimes ever seen in this country."