A judge warned serial drink-driver Warren Jenkins would kill three years before he caused the fatal smash that left a Kerikeri mother dead.

Judge Lindsay Moore QC lamented that he was unable to impose a sentence of preventive detention at Jenkins' sentencing in 2007, according to a court file.

Jenkins was sentenced to four years in prison for killing Katherine Kennedy, known as Rin, on March 17 last year.

At the time of the crash he was disqualified from driving, had almost twice the legal blood alcohol limit and had 16 drink- drive convictions.

Kennedy's friend Gerald Waters is lobbying Justice Minister Simon Power for harsher laws for recidivist drink-drivers.

"I'm all for rehabilitation but you only give a violent offender or a sexual offender three chances, why not drink-drivers?"

Waters wants the Government to consider preventive detention for repeat drink-drivers.

And he said he was working to a deadline.

"Realistically, this guy will be out in three years and eight months and that's my time limit. Once this guy comes out there's nothing at all that can be done, in fact it's even more likely he will reoffend in the same manner. And chances are he's going to kill himself or someone else. Nobody's safe."

The court file, released to Waters with Jenkins' permission, also revealed that on release from prison for his 12th drink-drive offence, Jenkins used his Steps to Freedom grant - a payment to help prisoners start their lives on the outside - to buy a car and alcohol.

Three days later he was arrested for drink-driving.

The file also showed that Jenkins had been charged with drink-driving at an average rate of once every three months since 2005.

Jenkins had just been released from prison when he hit Kennedy's car head-on.

She died later in hospital. Her then 5-year-old son Matthew was taken into the care of his uncle, Chris Kennedy.

The court heard that Jenkins was a chronic alcoholic who suffered a brain injury in 1994 when he was shot in the head.

In sentencing him to 18 months in prison at Whangarei District Court in March 2007, Judge Lindsay Moore QC told Jenkins he would have liked the option of locking him up indefinitely.

"Your circumstances make it plain that you are an ongoing risk to the lives and safety of everybody who uses the road," he told Jenkins.

"You are a man who does not merely drink a little bit over the limit and then drive.

"You are somebody who has been caught on many occasions at high levels. Levels of the sort which mean, almost inevitably, you are going to finish up killing yourself or somebody else or both. Statistically that is overdue to happen."