A police plan to pay people to dob in those selling booze and cigarettes stolen in armed hold-ups is likely to fail, a criminologist says.
Police are running a month-long campaign as they try to crack down on violent crimes in some communities across the country - particularly South Auckland.
They are offering to reward people who provide information that leads to a successful prosecution by calling into their Crimestoppers line.
The scheme is another tool to curtail violent crime against dairy owners, Police Commissioner Mike Bush said.
"A lot of these robberies are to order - there are people out there trading in the black market in terms of what's stolen.
"We'll turn up the heat ... until we turn this around," he said.
The reward would be several thousand dollars, depending on the level of information, Mr Bush said, but offenders would not be rewarded if they came forward.
The anonymity and safety of people who came forward would also be paramount, he said.
The reward campaign will run until the end of June.
Crime Prevention Group spokesperson Sunny Kaushal said the police were starting to take dairy owners' concerns seriously by offering rewards, creating a special task force and putting highly visible officers on the streets.
"The reward linked to the information will certainly help in getting to that underbelly," Mr Kaushal said.
But a criminologist at Victoria University, Trevor Bradley, said a lot of people close to the crime were unlikely tell the police about it.
"The types of people that have the information police are interested in are usually involved in tight-knit relationships with the people police are interested in," Dr Bradley said.
"They are reluctant to divulge information that might damage them."
Some people were afraid of dobbing in an offender, he said.
"More broadly, there is the psychological impact of being outed ... as a police informant.
"Among some sectors of the community, that's the lowest of the low."
A reward would need to be significant to compel people to come forward, he said.