LOL..... Did they check all the other bodies in the morgue for signs of life? can you imagine studying a dead body in a MORGUE and suddenly, your subject starts breathing?! That's like, straight out of a horror movie. That would be so freaky.
If they declared him dead at the accident site, they may have been in too much of a rush to notice a shallow pulse. A badly injured body that's not moving or breathing looks dead to me, lol. They might have felt no pulse and moved on to save someone elses life....
My Dad is a hospice nurse, he drives to his patients house and cares for them. Most of his patients are elderly and ALL of his patients have been diagnosed with terminal illnesses. He makes sure they're being fed properly and taken care of by the family, and that they're comfortable on meds until they pass. He always gets calls in the middle of the night when his patients die, he has to go to the house and pronounce them "Dead" I once asked him WHY he had to do that... couldn't they see the person was dead? Well, we were joking around and his response was "Yeah, but they like to hear from me 'Yep... they're dead!'" His more serious response said that vitals have to be taken and its a big rigamorole that has to be gone through when pronouncing someone dead. Maybe the medics at the scene were in too much of a rush to properly "pronouce" the man dead?