SUDDEN deaths among people being held by police in California increased sixfold in the first year after police departments there began using Taser stun guns, according to a survey by the University of California, San Francisco. The finding appears to back Amnesty International’s view that Tasers are a threat to life.

Taser International, which makes the weapons, says that the study is flawed because it relies on “suspect data sampling” from a limited number of police departments.

The researchers compared death rates in custody in the five years before and after the Taser was introduced. Death rates returned to previous …