Anna Guy, whose estranged husband Ewen Macdonald was cleared of murdering her brother, says her marriage was a sham.

Macdonald was sentenced to five years' in prison when he appeared in the High Court at Palmerston North last week on six charges he pleaded guilty to early last year.

Macdonald was cleared in July of murdering his brother-in-law Scott Guy after a trial at the High Court in Wellington. Mr Guy was shot dead in July 2010 in the driveway of his Feilding home.

Ms Guy, who returned to her maiden name after the trial, says she feels betrayed by Macdonald's lies and struggles to comprehend his actions.

"Getting arrested for killing Scott was one thing but there was way more stuff to come that was so devastating that no one knew about," she told the New Zealand Herald.

"I feel like a fool - it was total betrayal."

Macdonald admitted setting fire to the Guy family's old house in 2008 and vandalising Mr Guy's new home in 2009.

He also admitted poaching stags, killing 19 calves with a hammer, destroying 16,000 litres of milk and burning down a historic duck shooters' hut - crimes that all took place on three nearby farms.

Ms Guy says there have been times when she thought she would go insane if she thought about Macdonald's actions too much.

"I mean, we did things together ... What did that mean to him? Was it real? You start to doubt," she said.

"He had been through so much with us as a family - then it was like he was a traitor, sort of."

The pair, who have four children aged under nine, married in 2001. Scott Guy was the best man.

Macdonald, 32, has been in custody since his arrest on April 7 last year, and has spent 17 months in prison.