Doctors know he died of a heart attack, right? And he's not actually Tony Soprano, so the chances of someone secretly killing him and making it look like a heart attack are small. So what's the point? Accuracy, says David Dobbs at Nautilus. Research shows that doctors make a lot of mistakes when it comes to assessing death. Fifteen-to-thirty percent of the time, diagnoses of death are incorrect. Five-to-ten percent of the time, that mistake contributed to the patient's death.