The law in California rightly allows for the fact that a layman may not have perfect perception in terms of an assailant's capacities.
The standard is whether a "reasonable person" would believe s/he was in grave danger of death or bodily harm, NOT whether a trained physician or forensic expert would think so.
Per the link on the OK case, the prosecution believes the actions of the pharmacist prove he knew he was no longer in danger after the robber was incapacitated. I've already acknowledged that we don't know what the defense will argue.
Well that prosecutor also apparently believes that someone who had just had a gun pointed at them will be in a perfectly normal state of mind since the pharmacist is charged with first degree murder.