 The prosecution later demonstrated that blood is only visible under a microscope.He also admitted that blood evidence was collected in plastic bags, not paper bags as recommended, and stored in a police van without being refrigerated for up to seven hours.Scheck aggressively tried to shake Fung's time line about when he received Simpsons donated blood, hoping to show that police actually delivered it the following day, June 14, instead of June 13, giving them a whole day with Simpson's blood they could allegedly use to frame him.