He might have thought he could keep the lies hidden...but I think it goes deeper...I don't think he wanted to live with her knowing he was not what he pretended, that her not pursuing her graduate studies was on hold because of his fantasy college attendence, graduation and fantasy med school acceptance...
Her knowing eyes were too much and so he closed them...I read another poster say.. "The sound was too loud and he had to turn off the radio"...His "double life" is yet to be revealed... whether he had other secrets...
He has a personality disorder but he is not insane in the legal sense IMO...In Utah the usual insanity plea is "guilty but insane" with a person serving remainder of sentence in jail if they get well in the psych hospital...I don't think he can plead insanity.
That is probably the very first logical statement that I have read about his "issue".