Professor Dan Markel's young sons must have suffered short-term psychiatric impairment when so cruelly wrenched from their father; their home; and other familiar anchors. Then in July 2014, they must have suffered permanently when Daddy was never ever seen again. How cruel.

Psychiatric impairment is defined in terms of the degree of loss of total functional capacity that is directly related to a definite psychiatric illness.
Disability, although related to impairment, is a different concept. Its meaning implies disadvantage, restriction, or more frequently, the inability to pursue an occupation because of physical or mental impairment...the determination of disability is considered to be legal or administrative as opposed to a medical determination of impairment. (Thomas, R.B, "Psychiatric impairment and disability", The Psychiatric Forum, Vol.23, Spring 1973, pp 22-24).

The point is, that in criminal law, the forensic psychiatrist is looking to deliberate any signs of impairment of competency, but it is the law that determines legal competency and any degree or percentage of disability.
Only time will tell-in this case.