I read the article but could not find any pointers to evidence. It just said that with the technology available at that time it was possible for him to use opt

I read the article but could not find any pointers to evidence. It just said that with the technology available at that time it was possible for him to use optics. There is a big gap between that statement and the claim that he did actually use it. He had the means to by a gun, hence he is the murderer. May be there indeed is mounting evidence, but I could not catch it in the article. Unless by evidence the author means the scale of his detailed portraits, but that has been known for a while.