Yes, there are flaws in the system. Is it justice that a guilty person gets off because they are exploited? Say that knock out guy gets off because he claims he didn't hear his rights read because there was ambulance blazing by at the same time (true story), would that be justice? If a cop makes a mistake in procedure or even violates the law that should be a separate case. He should be charged in a separated case. It should not distract from the fact that the prep was guilty.
"Justice" in and of itself is a very flawed concept. Justice has much more to do with personal bias and pre-conceived notions of guilt and less so with the workings of the judicial system. For example: Is it justice when someone murders your parent(s), and only receives a 15 year sentence with the possibility of reduced sentencing? For the law perhaps, but certainly not for the surviving family.
If a cop makes a mistake in procedure or even violates the law that should be a separate case. He should be charged in a separated case. It should not distract from the fact that the prep was guilty.
Indeed, law enforcement should be reprimanded if not prosecuted for failing to comply with established procedures.
However, since failing to follow proper protocol has the potential to influence the proceedings of a case, it should not be simply disregarded.
Guilt before the law can only be established when all established protocols are followed, and all rights are ensured.