Its long been that the human word is by far the least reliable form of evidence in any court case. Deliberate lying from guilty persons or false accusers is a problem of course, but this isn't even the tip of the iceberg.
If sociological inquiry compelled me to beat a nun to death with a shovel in front of a stadium full of people, no two people out of thousands of witnesses would give the same description of me to the police. Ask any cop yourself and he'll tell you the same thing. Human beings tend to perceive passing glances of strangers to be much more accurate then they are. The human brain is morbidly obsessed with 'knowing". It has a hard-wired intolerance for ambiguity that is usually subconscious. The only way police "know" that witnesses are talking about the same person is if they generally agree on the most obvious physical characteristics; skin color, hair color, some unavoidably noticeable deformity, etc. Have you ever heard a conspiracy theorist make a big deal out of the fact that witnesses to the Tippet shooting described Lee Oswald as fat, bald, middle-aged, etc? Nothing at all suspicious, as it turns out. This is the norm.
To make things worse it turns out that all of the supposed walls between the rational brain and the emotional brain have never existed, and that imagining is essentially the same mental process as remembering. If I were to hold someone else in such contempt that I wouldn't be remotely surprised to hear that they killed somebody, it becomes very easy to start daydreaming about the hated foe doing just that, and then to become convinced that this daydream was a real-life murder that I was witness to. Real-life cases of this scenario are abundant. Just think of the elderly parents thrown in jail because of middle-aged children who suddenly remembered a hellish childhood of rape thanks to a "repressed memory specialist," or the child who feels he's disappointing an authority figure when a detective sternly asks him if he's "really sure" that his teacher didn't touch him inappropriately.
There is a scientific probability bordering on certainty that you, I , and everyone around us knows something that isn't true. The brain's hatred of ambiguity is just that strong, even for those of us who know it's there. So it goes without saying that people don't like to be told that they probably have a false belief or two, and when people hear a fact that's either unpleasant or frightening... Well, let's put it this way; global warming is a lie because Al Gore thinks he's better then me. Need I say more?
Why do I bring up Al Gore of all people? Well, it seems that the forces of intolerance for ambiguity and delusion are especially strong in societies that are educationally underachieving yet materially prosperous. Welcome to America, land of the spoiled, stupid, and clinically insane. The land where respectable conservative columnists cite Jack Bauer as justification for real-life torture with perfect, blissfully unaware sincerity.
Which finally brings us to our point; The sacred and mystical criminal confession. Police know full well that forensic evidence is far more reliable means of discerning the truth of some ugly occurrence. Still they stay awake past their children's bedtimes and stress themselves into early graves trying to squeeze the confession out of a perp. Because they know that's what the jury cares about more. There are plenty of cops aren't above going Jack Bauer to get the confession, not because they are manfully outraged by the continued cries of innocence from a man who evidence says is obviously guilty. Oh no, at least not usually. The fact of the matter is that when police beat a confession out of a subject it is typically due to a lack of evidence. Because they know what a jury will care about more.
Once when I was watching television I happened across an interview of jurors who had convicted a man of rape and then some years later was proven innocent by DNA. Not a single one of the jurors could bring themselves to believe it. How could a man possibly confess to a crime he didn't commit.? I killed three hookers last night. I'm three hundred and fifty seven years old. The planet Mars is my stillborn daughter. How could it possibly be done?
In order to accept that there is nothing special about a verbal confession we must first accept that there is nothing special about our own words, that there is no mystical force of truth in our own mental processes or interactions with each other.
As long as there are people who blame Darwin for the Holocaust, this simply isn't going to happen.
And so all the constitutional safeguards, all the grand notions of innocent until proven guilty, are nothing but wet toilet paper in the hands of a species that is universally schizophrenic.