Bishop73

Answer: Nick also points out that the crime scenes are always contaminated. The evidence was probably contaminated by the cops.

Answer: The reason the DNA was inadmissible was not elaborated on. We're only told it was inadmissible because of the "exclusionary rule." Therefore, the judge in the case must have deemed the way the DNA was collected from the suspects was in violation of their constitutional rights. The why was not explained and anything would be a guess (something like when they were arrested and there was no probable cause to take a DNA sample). But it's seems more of plot convenience to move the story forward quickly. Clyde passing out had nothing to do with the DNA being inadmissible, it only meant his eyewitness testimony may be considered unreliable. Therefore the DA's Office was not willing to try both men using Clyde as a witness, but go with the plea deal.

Bishop73