Find me a nurse who went to prison for a negligent death who simply made an error instead of breaking process / overriding a safety protocol or some such. Mistakes are not negligence. Not doing something you are supposed to in order to prevent a mistake is negligence.
This is the gist of it. I didn't see anything to suggest she didn't have her taser and her gun on opposite sides of her body. She reached for the wrong implement in a moment of great tension and crisis. She didn't have time to think, she reacted.
New Years Eve 2009 a somewhat similar event happened near where I live, being a transit officer shooting Oscar Grant on a transit railway platform.
It was claimed that the officer intended to use his taser but used his gun instead. Below, from Wikipedia, it says the judge determined that the officer had both hands on the weapon, something he was trained to do with a pistol but not his taser. Manslaughter was the conviction and he served 11 months. There's no doubt in my mind that Potter had no intention to shoot.
"Rains argued during the preliminary hearing that Mehserle lacked the malice necessary for a murder charge and that he intended to tase Grant. A BART officer testified, saying that Grant and his friends had yelled profanities and did not obey her orders to sit down moments before Mehserle fired at Grant. She said she was fearful when she heard taunts coming from Grant, his friends, and passengers on the train.
[92] After the seven days of testimony, Judge C. Don Clay concluded that Mehserle had not mistakenly used his service pistol instead of his stun gun. The judge based this on Mehserle's statements to other officers that he thought Grant had a gun. He also noted that Mehserle had held his weapon with both hands, but he was trained to use just his left if he was firing a Taser.
[93] Mehserle faced up to life in prison if convicted of first-degree murder.
[94]"