Juror Four cannot change his vote because of the testimony of the woman. who claimed she saw the murder committed. What significant observation does Juror Eight make at this point?

From the text:

Juror Eight: I think it's logical to say that she was not wearing her glasses in bed, and I don't think she'd put them on to glance casually out the window .. . . She testified that the murder took place the instant she looked out, and that the lights went out a split second later. She couldn't have had time to put on her glasses then. Now perhaps this woman honestly thought she saw the boy kill his father. [Rises.] I say that she only saw a blur.