In his closing today, Kumar's lawyer Simon Lance said his client's actions were "unwise" but not illegal.
"He was trying to do some of the work that he felt others hadn't done," Mr Lance said.
Recordings of the phone calls played to court revealed Kumar asked his victim about her cat and her medication before asking if the rape had happened.
The woman confirmed that it had.
"He is not demanding, threatening or unpleasant," Mr Lance said.
But Crown prosecutor Alysha McClintock said Kumar used "carefully calculated statements" when he phoned the woman.
"This is a fragile woman and the Crown submits that Kumar clearly knew that from all the information he had."
She said it was significant that Kumar had introduced himself as a doctor working for a psychiatrist who had previously examined the woman.
Ms McClintock said Kumar hoped the woman would retract her statement or change her evidence.
Earlier Kumar told the court the woman had initially told police she had been touched. It was only later she told authorities she had been raped.
He said he was trying to refresh the woman's memory.
"It was just to get ... hopefully able to remind her properly, exactly as to what had happened ... just to keep the conversation going."
Kumar said he never intended to discourage the woman from giving evidence because she had already given evidence at trial.
"I had not been directed by any court not to associate or that it was illegal. I just wanted to know the truth and why she had changed her story."
But under cross-examination from Ms McClintock he confirmed that he was aware of the proper legal processes in New Zealand and that he had legal representation and a private investigator working for him when he made the calls.
Ms McClintock said Kumar had a "zero chance" of talking to the woman if he had told health workers who he was so he posed as a doctor.
Kumar agreed he could not have identified himself.
"If I made the call saying I'm a prisoner calling from Auckland prison ... The society is thinking prisoners are bad people and that's why they're locked up."
He denied a suggestion from Ms McClintock that had the woman said there was no rape, he would have told her to go to authorities.
Justice Geoffrey Venning reserved his decision.