“Here” is a medical website [pubmed.gov] with articles that discuss a form of spasmodic angina, caused by a spasm of the artery. If I’m reading it correctly (I’m not an MD), this is without apparent heart disease present (I.e., without plaque occluding the artery). The subject is: “Angina Pectoris, variant/diagnosis.”
Perhaps a light blow to the chest of someone with this disease could play some role in triggering a spasm strong enough to cause death, without apparent cause if the disease is otherwise undiagnosed. I’m strictly a “perhaps” contributor.
What you need is an MD or ME to answer your question authoritatively.
Well, I think we have established that yes, it is possible to kill a person with a single, not especially powerful blow. I vaguely remembered something like this from physiology class. Thank you all.
Furthermore, it is possible that a less than inspired autopsy might miss the cause of death. So, our 77 year old rape victim may have (admittedly inadvertently and with freakish good luck) may have killed her attacker (yeah, I’m calling it good luck).