Louisiana plans to use nitrogen gas to execute death row inmate Jessie Hoffman next week. Here's what to know about the method and why its controversial.

Death by nitrogen gas is currently permitted in four states: Alabama, Louisiana ... the state to execute at least four more death row inmates this year. Most recently, Kenneth Eugene Smith ...

An inmate in Louisiana has been ... Nitrogen gas had only been used in death row executions four times before Tuesday, all in Alabama. Last year, the method was used to execute Carey Dale Grayson ...