Corrections has upped the ante against contraband in its prisons.

Narcotic dogs have been used in prisons for 25 years, but as banned items have increased, so has the need to train dogs to detect them.

Senior dog handler at Waikeria Prison Maurice O'Connor has been working with detector dogs for the past 19 years and is only too aware of the importance they play.

CHRISTINE CORNEGE/ FAIRFAX NZ Corrections dog handler Maurice O'Connor with Radar.

There are two types of dogs that work within Corrections in New Zealand: narcotics dogs search for the main types of drugs, such as meth, heroin, cocaine, ecstasy and the softer drugs like marijuana, cannabis oil and hashish.

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The others, cellphone and tobacco dogs, have only been employed over the past couple of years. Once the prisons became smoke free in July 2011, items such as tobacco, matches, lighters all became valuable items in prison.

CHRISTINE CORNEGE/ FAIRFAX NZ Visitor vehicles are searched regularly for contraband. Radar dons booties to protect the car's interior.

Cellphones can be a major issue in prisons because of the damage they can cause.

"They can be used to intimidate witnesses, organise drug drop-offs, photograph staff, use the internet for all types of interests - virtually anything you can do with a cellphone on the outside. You can understand how valuable it would be to a person on the inside."

Detector dogs are set up to search property and people in any place in which the inmates have access.

CHRISTINE CORNEGE/ FAIRFAX NZ Four-year-old Radar is expected to work as a detector dog until he's eight years old.

A big part of the job is searching people coming on to the Waikeria prison grounds.

The prisoners can be searched at any time and any place where they work. Inmate cells are common places to be searched and this is often done randomly.

"Just because they come into prison, it doesn't mean they stop doing what they were doing on the outside. But we've got to try to stop them, so when they get out, they don't go back to what they were doing."

The dogs significantly contribute to finding banned substances among visitors.

"They don't stereotype. If you have a gang patch on, or wear a white collar, wearing a suit, have dreadlocks, or you are wearing a uniform, to them it doesn't matter. If you smell like drugs they will indicate."

They "indicate" by sitting still when they believe they've found a banned item. They are usually rewarded for their work with some play time.

The TV programme Dog Squad has caused a noticeable decrease in people attempting to smuggle things into prison, as a lot of people didn't realise the facilities had detector dogs until they saw them on the show.

"People who visit the prison started cleaning their cars out and are now more careful about what they bring in, so my statistics have dropped dramatically. I'm not saying they not bringing drugs - they're just more careful about it."

The training of detector dogs begins when they are puppies. It takes about 12 months to get the dog signed off and operational, the working life is eight years, at which point the dog is rehomed.

There isn't a specific breed that is preferred.

"We tend to stay away from dogs that look intimidating, because we have to search children and members of the public. We are looking at dogs that have extremely good hunt drive. For that we use labradors, springer spaniels and german shorthaired pointers."

Numbers released under the Official Information Act show contraband finds have decreased in the year to September 2016 when compared with 2015/2016.

Waikeria Prison had only seized six items of alcohol instead of the previous year, which was 22. Communications devices number three in 2016, down from 11. Drugs went from 48 seizures to 10 and drug paraphernalia was also down from 15 to three. Tattoo equipment seizures decreased massively - 33 down to four - as did weapons - 30 down to six.