Like we have so little information about his past. I believe he is a math professor in series. He is genius and probably insane my question is how did he become a consulting criminal ? Did he worked for intelligence services in past or did he teach math in university. Whats your thoughts ?

And other theory that he may be bisexual, His talking and acting is quite feminen, And disguse himselfs as a gay man for no reason at all he could just intrduce himself by a normal guy,Jis word plays are quite wierd like "honey" he uses to Sherlock. When in court he flirts with a woman police officer so he may be bisexual but thats not important