How much is information that nets a killer worth?

Every year, a handful of transactions so secretive police won't discuss them are conducted with shadowy characters.

Figures reveal police are paying hundreds of thousands to informants every year for tips to help them solve crimes.

The figures, released under the Official Information Act, showed police paid $301,772 to informants in the 2014/2015 financial year.

Since, they have paid $68,991 between June 30 and December 2, 2015.

Payments to informants are approved by district crime managers, who hold the rank of Detective Inspector, and approve money within the police budget, said acting national crime manager Inspector Paul Berry.

Police refused to divulge the largest amounts of money paid to their sources – saying airing such information would be likely to affect investigations.

According to the Police Association, the practice is simply a routine part of good policing.

Mike Gillam, a private investigator at Thompson & Toresen,who began his career as a police officer, said informers were traditionally recruited either through police "handlers", who identify people willing to pass information then broker their tips, or from suspects who want to use information as a "bargaining chip".

Some criminal informants also began passing information to the police out of a sense of integrity, he said.

"Presumably they find their moral compass somewhere along the way."

Informing was a dangerous occupation, as their peers were likely to mete out punishment if their status was revealed, Gillam said.

"It can be pretty brutal, which is why the police have to be so careful.

"The only thing you have to do to is go into any police cell or custody unit and see the inscriptions on the cell walls 'Joe Bloggs is a narc', 'John Doe is a rat' – they let everybody know."

It was a popular misconception that informants only worked with undercover cops, asfrontline constables on the beat would have street-level informants as well, Gillam said.

They most likely would not be paying for information, but police did pay trusted sources with whom they had built up a "rapport" for everything from a "few hundred for information on a string of burglaries" to much more for information on serious crimes like murder.

Informants were usually paid in cash or into a secret bank account , Gillam said.

The police figures showed informants were paid $343,057 in 2010/11, $416,114 in 2011/12, and $295,336 in 2012/13.

Police Association president Greg O'Connor said paying informants was an accepted and almost routine piece of police work.

"Good police officers have good informants, if it stopped, it would be to the detriment of the public."

He said informants put themselves at risk by giving police information, so they should be rewarded.

O'Connor, formerly an undercover officer, said the money spent was a small price to pay for police to give a good service to victims.

Police were asked why police payed their informants, how good the information had to be, and how they ensured they were not being ripped off.

But Berry refused to elaborate, saying only that not all informants received payment from the police.

"Information is vital to police investigations and police rely on a wide range of people from the community for assistance. Whether an informer receives any payment will depend on a number of factors, but mainly on the 'value' of the information to Police and the community."

Asked if he thought there were ethical issues with police swapping money for information, Gillam said if the public knew how many crimes had been solved due to such relationships they might back the transactions.

"I think the police do a great job with their informants. I don't think they're giving away cash willy-nilly."