I've worked in ERs before and am somewhat familiar with the process they use for determining brain death. There was a child that came in with catastrophic brain damage, and the process to determine that the child was in a permanent vegetative state was quite extensive. There were multiple evaluation by neurologists and neurosurgeons via MRI and EEG over the course of multiple days to verify a lack of brain function. It's not something that is determined in the moment. The decision made in the ER is whether or not the organs will be donated because it can make some differences in the life-support care during the brain death determination process.