I personally like to look at the most common CODs for someone the victim's age. So for men David's age, we have:
1. Cancer 25.6%
2. Heart Disease 23.8%
3. Unintentional Injury (eg accident) 9.5%
4. Chronic Liver Disease 4.5%
5. Diabetes 3.9%
6. Suicide 3.6%
7. Lower Respiratory Diseases 3.4%
8. Stroke 3.1%
9. Septicemia 1.4%
10. Kidney Disease 1.4%
Find links to current and previous listings for the leading causes of deaths for males in the United States
www.cdc.gov
So for a man David's age, it's over 67% likely that he had a medical event, 9.5% likely that he had an accident resulting in death, 3.6% likely that he self-harmed, and less than 1.4% likely that he was a victim of homicide. I use these numbers to inform my sleuthing, so unless there are obvious signs of foul play, foul play is ALWAYS below accident/self harm in my list of theories. Most people with severe medical issues aren't well enough to disappear, so that factors less, but I always include cardiac issues in my theories for middle aged folks.
I've long wanted to do an informal study of case resolutions on WS, but I haven't yet. So you'll have to take my word that outcomes follow the probabilities listed above.
Note: For men 1-19, homicide is .1% more likely than suicide, but sadly I think that is due to several mass shootings.