Answer:
The right to due process provide American citizens with the chance to receive fair application of the law before they can be indicted with their sentence/punishment.
Cross-examining evidence is a very crucial part of the fair application of the law. By suppressing a certain evidence, we take away the ability of the defendants to fully proof their innocence in the court. This might caused them to be punished for the crimes that they never did. This is a clear violation of constitutional right to due process.