No. He got away with forgery. He didn't kill her, cancer did. Even if the stresses of flight hastened her demise by a few moments, that could likely only be stretched to elder neglect, or involuntary manslaughter. I don't know what jurisdiction you landed in, but most communities would be hard pressed to field a jury willing to imprison a man for trying to help his dying wife get home, regardless of how traumatizing it was to the flight crew.

Back on topic, there are several conditions (though none should be considered "seriously" ill) that are not contagious, but can cause fevers and make flying absolutely miserable. sinusitis, ear infections and dental abscesses probably being the most common. In these instances, it might help to ask your physician to specifically state in a note that flying could exacerbate your discomfort and possibly cause long lasting harm.

If you are seriously ill, you need insurance. i know the OP doesn't buy it, but he should. Travel insurance will pay for a nurse or paramedic to fly with and take care of you. Further, if you are too sick to fly with an escort, they will fly you in an air ambulance.