5. Finally, are the police really that corrupt and/or stupid? Go back up to Professor Duane's hypothetical in which a suspect protests his innocence, and Duane imagines that Officer Bruch -- Professor Duane's real-life co-presenter in this talk! -- takes five words out of context and testifies in court, "He confessed to me, 'I never liked the guy'."
The phrase "Anything you say or do can and will be used against you in a court of law." would not exists if this were not the case.
When the real Officer Bruch gave his 'rebuttal', he started out by started out by saying, "Everything he just said was true. And it was right, and it was correct." If I had been in the room at the time, I would have asked him, "Seriously? Were you listening when Professor Duane said that if a suspect protested his innocence in the way that he described, you would take that out-of-context quote and only tell the jury that he said 'I never liked the guy?'" Well, we already know that George Bruch didn't really agree with everything that Professor Duane said, since Bruch contradicted him on some points, such as Duane's claim that "talking to the police cannot possibly help you even if you're innocent". But I would have liked for Officer Bruch to say if he thinks the police are anywhere as stupid and corrupt as Professor Duane was implying that they are.
My favorite example is Verbal Judo , which is about how to lie (while conving yourself that you are not lying) in order to manipulate people. It was published by a former police officer, and is used in training courses for police departments around the country. Ostensibly the reason is for defusing domestic violence through words.
More to the point -- and I went into this in my first article about the Fifth Amendment -- if the police and the courts are even remotely that corrupt and incompetent, then that's a wide-ranging problem that applies to all types of evidence gathered in the case, not just statements from suspect. And if that's the case, then the Fifth Amendment is just a band-aid that only solves the stupid-cops-and-courts problem as it applies to suspect statements specifically. It doesn't solve the problem as it applies to circumstantial evidence, unreliable eyewitness testimony, false memories, evaluating the credibility of other witnesses, and other factors.
In other words, if you're arrested, suppose the cops really are so dumb and/or evil that they would quote your "I never liked the guy" out of context to try and get you convicted. So, taking Professor Duane's advice, you say nothing. Do you still trust those same police officers to handle the other aspects of your case fairly? To make sure any exculpatory evidence is brought to light? To interrogate other witnesses without leading them towards a pre-set conclusion?
No, that's why there's also a right to legal representation.
As I said in my first article, that doesn't mean that this is not a valid argument for the Fifth Amendment. But it means that if this is the primary argument in favor of the Fifth Amendment, then what the people making this argument are really saying, is that the whole system is broken.
The system was broken before the constitution was created, and the Bill of Rights serves as a patch over the corruptions of the legacy system.