The son of an Indian woman police allege was murdered by her jilted lover has told of his aggressive phone calls leading up to her death.

Shanal Sajesh Kumar, 29, has pleaded not guilty to murdering his lover, Dipti Patel, 42, with a skipping rope in her New Plymouth garage on Gaine St in New Plymouth about April 7, 2009.

In the High Court trial at New Plymouth Kumar's lawyer, Peter Winter, has accused the dead woman's husband, Mukesh Patel, of his wife's murder.

The Crown has said it will prove that Kumar murdered Mrs Patel and tried to cover it up as a suicide by hanging.

Yesterday, Mrs Patel's son Nainesh Patel, now 21, and an accountancy student at Victoria University, told the court how his father received a phone call at his work in early 2009.

A man speaking Hindi told Mr Patel his wife was having an affair.

Mr Patel left work for home, called his older son into the sitting room, telling him he was old enough to hear what was going on.

In front of Nainesh Patel, then 17, Mr Patel asked his wife if she was having an affair. She did not reply.

Nainesh Patel said his father, who was a calm man, had raised his voice a little but remained in control.

His father became frustrated and confused when his mother did not respond. She showed no emotion to his repeated questioning.

His father asked him to ask his mother whether she was having an affair but she still did not respond. His father returned to work.

Nainesh Patel said it became clear soon after that his mother was having an affair and it was with the accused.

The family were getting a lot of phone calls from Kumar who would tell his father to give him his wife.

About March 2009 his mother said to tell Kumar she didn't want him to ring any more. Kumar demanded she returned his keys.

Nainesh Patel said his father did not want to see Kumar and sent him out to give him the keys.

He was aware his father and mother were talking about separating, and wanted to remain on good terms. The two boys were to stay with their mother.

His mother had told him several times she was terrified of Kumar and asked him if he would like to shift to Palmerston North. She told him that Kumar had threatened her that he would find her no matter where in the world she went.

"She was scared and worried. There was a lot of blackmail and threats and she was afraid. She said the relationship was based on blackmail."

Kumar would tell her if she tried to get out of it he would expose her and let everyone know about their affair.

She had told her older son with tears in her eyes that she regretted what happened.

To questioning from defence lawyer Peter Winter, Nainesh Patel said his father was never angry but he was upset about the affair.

Kumar had never told his father to treat his mother well.

He did not notice his mother losing weight. He agreed she was sad and scared before her death but not depressed.

The trial continues.

- © Fairfax NZ News