Toronto's police overseers say they don't know enough about the costs and risks of Tasers to approve the 3,000 stun guns requested by the chief.

The Police Services Board has asked Chief Bill Blair to provide a detailed business case for the stun guns, and a legal and medical review of their impact in other jurisdictions.

Tasers are used to subdue people with a jolt of electricity.

At a board meeting on Wednesday, Blair had asked to expand access to Tasers to frontline officers at a cost of $8.5 million. The force is testing the equipment in a pilot program.

Tasers are handheld devices that deliver a jolt of electricity — up to 50,000 volts — from up to 6.5 metres away. The shot can penetrate five centimetres of clothing.

The jolt causes an uncontrollable contraction of the muscle tissue, immobilizing the person and making the suspect fall to the ground — regardless of pain tolerance or mental focus.

Blair told the board he believes Tasers will save lives and are an important use of force option.

The weapons have been controversial in other jurisdictions. There have been several accounts of deaths involving Tasers, but the exact cause of death is often contentious because the suspects often intoxicated at the time they were subdued.

Provincial regulations only allow the Toronto stun guns to be handled by about 450 police supervisors. The province would have to amend legislation before Tasers could be handed out for widespread use.