Will Major Hasan successfully use PTSD as a defense, or will it at least become a mitigating factor to be considered. If the trial is at Fort Hood, as seems likely at the moment, many of the Members (jury) panel will already have quite a bit of extra-judicial information.
Here are some links relating to secondary traumatization.
Zimmering, Munroe, & Gulliver, Secondary Traumatization in Mental Health Care Providers, 20 Psych. Times (Apr. 2003).
KevinMD.com, Did Nadal Malik Hasan suffer from compassion fatigue or vicarious traumatization? 6 November 2009.