When the nurse is a victim, it's determined that the syringe used to kill her was injected under her fingernail. Now in order for the killer to have done this, he would have had to have knocked her out first which would've showed signs of trauma during the autopsy.
We saw the nurse enter a room with the killer right behind and the next shot was of the next morning. We conveniently don't get to see just how he accomplished this feat of injecting the syringe into her fingernail.
The nurse would have immediately put up a struggle so it would have been near impossible to get the syringe into her fingernail unless he asked her to give him her hand and not to move it.
So the only plausible way for this to have occurred was to knock her unconscious and then inject the syringe, but knocking her out would have shown signs of trauma in the autopsy. It's too giant a plot hole to ignore.
We saw the nurse enter a room with the killer right behind and the next shot was of the next morning. We conveniently don't get to see just how he accomplished this feat of injecting the syringe into her fingernail.
The nurse would have immediately put up a struggle so it would have been near impossible to get the syringe into her fingernail unless he asked her to give him her hand and not to move it.
So the only plausible way for this to have occurred was to knock her unconscious and then inject the syringe, but knocking her out would have shown signs of trauma in the autopsy. It's too giant a plot hole to ignore.