The Sixth Amendment to our Constitution reads in part: "In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial…" of which, none of this actually currently exists in the form of which it was intended. That is to say, those that are accused of crimes certainly do not have a speedy trial, in fact, as reported by the nytimes.com, sadly: "97 percent of federal cases and 94 percent of state cases end in plea bargains," of which, plea bargains aren't a form of a public trial, in fact, they are the very opposite of such, and are best considered to be "backroom" deals.
There are many, many reasons why plea bargains are so prevalent in this country, to which, it all begins with the fact that if the sheer quantity of arrests far exceeds the capacity of the courts to deal with such, plea bargains, become a necessary evil. Additionally, when the criminal justice system over penalizes the accused to such an extent that even relatively modest "crimes" are subject to significant incarceration time, than the defendant to those crimes, is placed into the unenviable position of essentially risk management.
The thing that makes plea bargains, especially insidious, is that the prosecutorial element of the justice system, are not bluffing, when they indicate to the supposed perpetrator of an alleged crime, that failure to take a plea bargain, will often result, if convicted, in substantial incarceration time. Additionally, the criminal justice system isn't fair on an entirely different level, which is the State or the federal government can, if so desire, in cases that pricks their interest, bring forth the full force of such prosecutorial resources against the indigent or vulnerable, almost without limit, whereas a significant amount of defendants simply don't have the monetary resources, nor the connections, nor the comprehending of the intricacies of our American justice system, to even do much better than to accept a public defender, which equates to, unequal justice.
When it comes to plea bargains, it is highly unfortunate, that these deals are even done in the first place, as this means, by definition, that the accused never gets their fair day in a court of law, but must instead, if they are prudent, along with hopefully having an intuitive understanding of risk management, make a deal, because that deal , all things considered, is, not only the best way to manage their risk, but that deal is known and knowable, whereas an actual trial could easily result in substantial penalties that would effectively end the defendant's options for even an okay life on the outside, although, in theory, the defendant could risk all, to gain all, and thereby obtain his freedom.
In a nutshell, plea bargains are constructed so as to lure the guilty as well as the innocent, to strike a deal, in order to take a reduced punishment that often though bad enough, will allowed such defendants to live to fight another day. In point of fact, plea bargains should be looked upon for what they essentially represent, which is the bullying and the intimidation by the state against those that do not have the resources or wherewithal to effectively fight back, leaving these defendants wounded and even more vulnerable to basically being treated as a class of citizen, that has reduced rights, and limited freedom.