Why Tasers sometimes fail to stop suspects — and what weight has to do with it

Multiple Taser deployments failed to stop Pamela Cisneros, 49, during a roughly four-minute standoff in Times Square last Monday, after she allegedly stabbed two people. The attack left a 32-year-old woman dead and a 68-year-old man wounded.

"As multiple officers discharged Tasers, which proved to be ineffective, the subject continued to advance toward our officers with the knives," Jessica Tisch, New York City police commissioner, said in a news conference that evening. 

When the Tasers failed to subdue Cisneros ...