A former ambulance driver who indecently assaulted vulnerable patients in the back of his ambulance understands the pain he put them through but isn't sure why he did it.

A pre-sentence report for James Brent Henderson said he showed "insight" into his offending on three different women and was "definitely of the view he shouldn't have done what he did".

However, at his sentencing at the Auckland District Court yesterday, Judge Philippa Cunningham said the appropriate thing to do was for him to undergo a psychological assessment to discover what caused him to offend.

The assessment was ordered as part of his sentence of nine months of intensive supervision. Henderson was found guilty by a jury on five indecent assault charges last year but the convictions were quashed by the Court of Appeal and a retrial ordered. The 36-year-old pleaded guilty to three counts in October after the Crown agreed to drop the remaining charges.

Each one related to incidents that took place over a nine-month period in Auckland in 1999. The judge said all the victims were "vulnerable" woman who needed medical treatment by Henderson, who was in a position of trust. The pattern of offending also showed a level of pre-meditation. "The extent of the harm to the victims is another aggravating feature. The effects on all of the victims is quite extensive. One appears to have started to act out when she was unable to tell people what happened.

"She now seems to have feelings of guilt about how she acted and treated people at the time. The second victim felt vulnerable, fearful and dominated in the back of the ambulance."

The third women changed her job, struggled with relationships and had self-esteem issues.

One of the victims was a schoolgirl who crashed her car and was being taken to hospital when Henderson pulled up her skirt and touched her.

Another collapsed while she was running and woke in Henderson's ambulance as he exposed her breasts after he lifted her bra and T-shirt up. She complained about him as soon as she arrived at hospital. The final victim said Henderson put his hands on her genitals as he asked her if the touching hurt, and didn't move his hand when she looked at him.

Judge Cunningham hoped a period of supervision would allow him to get "get back on his feet and once more be a productive member of society".

She said he would never work as a nurse again and hadn't had an easy life since the offending.