When you're innocent you don't fear any interrogation..regardless of how ruthless the interrogator might be.OTOH when you're guilty you know you have to lie and evade and even the most skilled liar can't remember all the lies.
Yes,I know that defense lawyers say "*never* talk to the police" but when you take the 5th that suggests that you have something to hide.
There are so many laws and rules that if investigators and prosecutors look long and hard enough, they can always find a violation or crime.
Show me the man, I’ll find you the crime.