There's an easy way you can help police catch thieves if they rob your house.

Keeping a record of a product's serial number, using DNA marking or an invisible pen increases their chances of finding stolen goods and apprehending the burglars.

Officers like Wesley Dabb are out every day checking through the records and shelves of secondhand dealers.

The New Zealand Police work closely with secondhand dealers and scrap metal merchants to find stolen goods.

"We randomly check for serial numbers to make sure nothing has been stolen."

Most dealers are happy to help weed out their dishonest customers and regularly supply their register of customers, he says.

Under the The Secondhand Dealers and Pawnbrokers Act shop owners are required to take the details, including photo identification, of anyone they purchase articles from.

They are then required to hold those articles for 14 days before they can be onsold, so the police can easily match up burglars to stolen property. They also check the shop's records for further clues, Mr Dabb says.

"I look for high purchases that they have made and if it is from a known burglar I will highlight that and forward it to the Tactical Crime Unit."

If it is deemed appropriate, a search warrant is applied for and a visit is paid to the burglar's house.

The police have made some arrests from their checks but the arrests do not happen as often as people may think, Mr Dabb's boss Sergeant Phil Patterson says.

"A lot of that is down to victims of crime not recording serial numbers.

"If they are not recorded then they are never going to flag up in our system as stolen."

He encourages people to use snap. org.nz to record their property's identification numbers or to use DNA marking or invisible pen on it.

"If every single person recorded every single serial number I guarantee you would find a lot more stolen goods in the secondhand dealers."

Police would also be able to attribute more thefts to criminals when houses are raided, Mr Patterson says.

The police come across a lot of items that look like they do not belong in properties when issuing search warrants, he says.

"Sometimes people are on benefits and not working but there are items in there that look like they don't really belong.

"But if we can't establish it is stolen property we can't do anything with it," he says.

Manurewa acting area commander, Inspector Richard Wilkie encourages people to pass on what they know through the anonymous Crimestoppers line, 0800 555 111.

"This is for people who may know someone who is involved in stolen property, such as family members, friends, work colleagues or other acquaintances and for some reason they feel they can't take the information to the police."

- © Fairfax NZ News