Mark Lundy a bad actor who tried to lie his way out of jail - Nigel Latta

Mark Lundy is a bad actor who tried to sell an "impossible" lie to get away with murder, well-known psychologist Nigel Latta says.

The brutal killings of Christine and Amber Lundy shook the nation. Source: 1 NEWS

Nigel Latta Source: 1 NEWS

After a seven-week re-trial and 16 hours of deliberation, a jury at the High Court in Wellington yesterday found Lundy guilty of the murders of his wife Christine and seven-year-old daughter Amber Lundy.

He was sentenced to at least 20 years in prison.

Latta, who profiled the Lundy case for his TV documentary seriesBeyond the Darklands, has told RadioLive there is no doubt that Lundy is guilty.

The story Lundy offered police - that a burglar had committed the murders after being interrupted in the course of a crime - is implausible, Mr Latta says.

"His story just didn't make any sense. It's possible if a burglar might kill someone if they're discovered in the course of their burglar but not in the way that Christine Lundy was killed," he said.

"Someone tried to obliterate her. Someone spent a long time. The attack on her was sustained and incredibly violent and very personal. And also, a burglar wasn't going to kill a seven-year-old in the house at the same time.

"What Mark Lundy was expecting the world to believe is that an incredibly violent, very personal, rage-filled attack, and then the burglar stopped that and though 'oh yeah, well I'll take a jewellery box as well'."

Mr Latta says "behavioural evidence" also indicates Lundy's guilt.

"His performance at the funeral was ridiculous. It struck people at the time.

"A funeral director at the time just was incredibly uncomfortable at how he behaved. This is someone who is around grieving people for a living. That's a job. And she was uncomfortable with how Lundy was performing."

Lundy's plan was always to kill both Christine and his seven-year-old daughter Amber, despite theories claiming Amber was only killed after witnessing the attack, Latta claims.

Appeals process may restart - law expert

Lundy may be able to appeal his latest conviction for murdering his wife and child at all levels of the court system, a legal expert says.

Canterbury Law School Dean Chris Gallovan told TVNZ's Breakfast that Lundy's second conviction may not end the already-lengthy legal saga.

"I think that what people have to realise is that after the Privy Council quashing of the conviction and granting of appeal, that really pushed the reset button," he said.

"So this trial was conducted as if the first trial hadn't existed. And just as he had a right of appeal after the first trial, he's got one after this as well."