Light passing through Slow Glass took longer than 'instantaneous.' It was discovered when car windshields were causing accidents because "I didn't see it" was true-- the image of an obstacle wasn't through the glass yet. But this brought up a new industry-- Slow Glass windows that had been exposed to 'scenic vistas' or other 'prime' images. The thicker the glass, the longer it took for the image on the 'input' side to arrive on the 'output' side. So, you could buy a 'window' with a view of the Grand Canyon or Niagara Falls. Only thing is-- the glass is 2-way. And someone committed a murder in front of a multi-year piece of Slow Glass. He argued in court that he was innocent, and that the glass would prove him innocent. Judge threw out that piece of evidence, and continued the trial. He was found guilty and punished appropriately. Story was about the judge who convicted him watching as the image of the murder came through the glass, and showed that he had really done it.