That statement is factually untrue. Law enforcement regularly withholds evidence without any repercussion. More importantly, the previous comment is referring

That statement is factually untrue. Law enforcement regularly withholds evidence without any repercussion. More importantly, the previous comment is referring to plea bargaining. Essentially, law enforcement is using the poor state of the current justice system to pressure people without resources into accepting a guilty verdict because the system is so stacked against them. Imagine: "Yeah, you can try to prove your innocence, but we're going to hold you until your arraingment. That'll be at least a few weeks, which will mean you'll lose your job and your apartment and your car will be repo'd. And you'll probably lose anyway, because we've got all this evidence against you, and we promise its bulletproof. Or... You can take this deal we're offering. You plead guilty, and we'll let you walk out of here today."