Police investigating Lee McMurdo's murder believe he was dealing a new drug.

McMurdo was found dead by his 12-year-old daughter Lateasha at his rural home, 10km south of Helensville on July 29, but it is believed he died on the morning of July 27.

The 32-year-old was last seen alive on July 26 at 1.40pm and police think his murder may have been an "unintended consequence" of a burglary or a debt recovery attempt.

STOLEN: This Mitsubishi Mirage stolen from West Auckland could be linked to Lee McMurdo's death.

Today police said they believed McMurdo, who has previously been charged with growing cannabis, was dealing MDVP known as "bath salts" at the time of his death.

The drug was new to New Zealand but was widely known in Scandinavian countries and parts of the United States, police said.

A North Shore man had to be tasered twice and then heavily sedated after taking the drug earlier this month.

In Toronto, two police officers suffered broken bones in their faces, hands and wrists after being attacked by a man who had taken the drug recently.

There have also been reports in the United States of a man skinning himself after taking it and another stabbing himself and throwing his own intestines at police.

McMurdo's father Bruce today released a statement saying despite almost a year passing "it doesn't get any easier, particulary as none of us understand why he died".

He said Lateasha was "really struggling to come to terms with losing the father she idolised" and McMurdo's two younger children, Bowen and Jazmin, don't understand why their father is not with them.

The children required ongoing support and counselling, Bruce said.

"Losing Lee has devastated our family."

He pleaded for anyone with information to call police.

POLICE BATTLE 'RUMOUR AND INNUENDO'

Detective Inspector Greg Cramer said police had interviewed more than 3000 in their hunt for McMurdo's killer and 18 detectives remained on the case.

"Police continue to make progress but at times it's a challenge cutting through the rumour and innuendo that has captured the local community. We have worked hard to filter the rumours to arrive at the facts," he said.

"Mr McMurdo was a known user and low level dealer of illicit drugs. It seems he was seduced by them as a means of escaping a difficult financial situation following the collapse of his business."

Despite not making an arrest over McMurdo's death, Cramer said the pressure detectives had put on the criminal community had resulted in numerous arrests for other crimes.

"A year of intensive investigation has had an impact on other criminal activities. Offenders have been arrested and a wide range of crimes solved.

"Stolen boats, cars, earth moving machinery and a variety of illicit drugs are among items that have been recovered, but of course our focus remains on apprehending the person or persons responsible for Lee's death."

Cramer appealed for sighting of a white Mistubish Mirage, with a black bonnet, that was stolen from West Auckland on the day McMurdo died and is believed to be linked to "events surounding" his death.

The car was driven north late on July 31 and is believed to have hit a cow in the Wellsford area, damaging the front.

Cramer was confident police would eventually solve the case.

"I am conscious that the passage of time affects relationships, friendships and allegiances among individuals and there are those in the community who know about this murder. Someone has the precise information that we need.

"If you know who murdered Lee Ross McMurdo, I urge you to contact the police immediately."

'BATH SALTS' A MIX OF DRUGS

The head of Auckland's metro crime operations and support squad, Detective Senior Sergeant Chris Cahill, said bath salts wasn't so much a new drug, rather a different version of existing substances made from whatever ingredients drug cooks could get hold of.

In the last three years drug dealers had used several similar substances to make existing and newly named drugs as the supply of traditional ingredients had run out, he said.

For example, party pills were now often sold as ecstasy.

Bath salts could contain any number of substances including MDVP, methadone or BZP, he said.

Cahill said police hadn't seized "a truck load" of drugs being sold as bath salts, but had seized a lot of illegal pills, some of which would have contained MDVP.

Anyone with information on the vehicle or McMurdo's murder is asked to call the Operation MANU investigation team on 0508 00MANU, Crimestoppers anonymously on 0800 555 111 or email opmanu@police.govt.nz.