The NSW Police is trialling unmanned drone aircraft, which if successful could be used in search and rescue and emergencies.

The police, with the assistance of the Civil Aviation Safety Authority, will run the trial using a range of models in a variety of situations.

The announcement has sparked concerns from civil libertarians, who want strict guidelines on when police can use such devices, to avoid having the aircraft hovering above the city watching innocent civilians.

But Assistant Commissioner Mal Lanyon said police were looking at using the devices primarily in place of helicopters and fixed-wing aircraft, to reduce costs and the risk to officers.

"RPAs [remotely piloted aircraft] could be equipped with video technology, including infrared technology, to aid police conducting search, rescue and emergency responses," Mr Lanyon said.

NSW, the largest police force in the country, is not the first Australian law enforcement agency to trial drones.

The Australian Federal Police already use the aircraft in big investigations but only at crime scenes where they have a warrant. One was used by the AFP during last year's search for the body of murdered anti-drugs campaigner Donald Mackay at Hay, in southern NSW.

Queensland and South Australian police own two each but have strict guidelines on how and when they can be used. Victorian police said they did not own or use drones.

Mr Lanyon said only trained and qualified operators would pilot the devices and strict protocols, procedures and legislative parameters were in place.

The NSW Council for Civil Liberties president Stephen Blanks said he did not oppose police using drones for search and rescue operations.

But he said the public must be assured they would never be used for general surveillance activity.

"If there are benefits which can be had from the use of devices like this in emergency situations then there should be rules in place which allow these devices to be used," Mr Blanks said.

"But we also need rules that make it absolutely clear how long recordings are kept for, when they are destroyed and notification of people who may be concerned about being captured by these devices."

NSW Police said it was conscious of privacy issues and had undertaken consultation to ensure it complied with privacy legislation.

"The use of new and emerging technology that is operationally effective and cost efficient makes complete sense," Mr Lanyon said. "The purpose of the trial is to ensure that any privacy concerns are considered and addressed prior to future deployment."