Footage from stun gun cameras is increasingly finding its way into civil and criminal cases, and prosecutors in Pennsylvania say it was the strongest evidence used to charge an officer this week in a man's shooting death.

Prosecutors in central Pennsylvania say Hummelstown police Officer Lisa Mearkle's stun gun captured images that showed she shot an unarmed motorist in the back as he lay facedown after a traffic stop.

Taser International says it's already sold about 80,000 stun guns with cameras, about 10 percent of all stun guns it's manufactured.

The cameras can add about $500 to the $1,200 cost of Taser's basic model.

Mearkle's lawyer says she kept her stun gun pointed at the man to document what was happening, not thinking it would be used against her.