I'm not too sure about the person being radioactive should they die from radiation poisoning. I've posted a link to Wikipedia which may help you. Also if you are able to find information about the impact of the atom bombs on Japan in 1945 they should help too.
Radiation Poisoning For the autopsy situation follow this link to an incident of a Russian security agency officier dying from a supposed deliberate radioactive substance poisoning this occurred a little over a year ago.
Alexander Litvinenko poisoning Hope this helps!
