This is so common anymore in trials. The defendant doesn't want to be held guilty and there are umpteen "experts" who will sell themselves to talk about this or that disorder. They can't ascribe it to the defendant, but the defense feels it is a good shot just to muddy the waters.
The only experts I really can give credence to are the ones who can say that they have interviewed the defendant and they can definitely say that they have or show this disorder.
Anyone can get up and talk about blah, blah, blah, but juries, most juries, are smart.
They can tell when an expert is just blowing smoke, imo.