With electronic stun guns now being used by a growing number of UK police forces, BBC News examines the controversy in North America, where a series of deaths have put Tasers under fresh scrutiny.

When Robert Bagnell died in Canada last June, his family were told he had suffered a probable cocaine overdose.
The truth emerged in fits and starts, however. They eventually learned that police had jolted him with 50,000 volts of electricity from a Taser gun.