Disregarding the ick factor of the following story, there is a claim on the part of the defendant, by his lawyer, of having PTSD. The reference to PTSD is sketchy at best, saying only that he served in the Navy 20 years.
Generally speaking, no one in the Navy would develop PTSD; but it goes to the specificity of the disorder itself that would make for the occasional exception.
Granted that, especially in World War II, Navy personnel fought in horrendous, even heroic battles on the high seas and today we have the Navy Seals and other Special Forces and Special Ops groups with boots-on-the-ground missions and engaging in many ground-based fire-fights. But the specificity of PTSD calls for a protracted, even constant exposure to the real threat of death.
So, in the most general of terms, just serving in the Navy in and of itself is not conducive of developing PTSD, but obviously the door remains open for the rare and extraordinary exception.