Prosecutors throughout the federal and state criminal justice systems do their work in extreme secrecy. Thus, they secretly interview witnesses, issue and enforce subpoenas for documents, review documents, send out teams of investigators and decide who to prosecute and who (their friends) not to prosecute. Of course, you don't really know what evidence the prosecutor has pulled together - evidence that might truly exonerate the target of the investigation - because everything is secret, including the prosecutor's mistakes and the prosecutor's intentional prosecution of criminal defendants for crimes the prosecutor knows the defendant or the defendant's wife or children did not commit. In many prosecutions the prosecutor "overcharges" by charging a defendant with crimes the defendant did not commit, to force the defendant to plead guilty to the other charges or face the impossible task of defending oneself on all the charges without being able to afford competent private counsel. Also, prosecutors often name innocent mothers, wives, children or other relatives to force the real defendant to plead guilty. There are hundreds of illegal ways for a prosecutor to force a defendant to plead guilty, and the prosecutor does all of these things in secret.
As the highest attorney in New York State, I would have the authority to investigate and audit the prosecutors to ensure that they were obeying the law (which of course they are not, because there is no effective oversight of prosecutors anywhere in the United States).
As a result, everyone pleads guilty, even (or especially) when they are not guilty under the standards of a fair trial. Also, this results in many more prisoners in jail as a percentage of the population than any other "civilized" country. The costs of this outrageous system (disregarding the executions of innocent people) are far more than you might imagine. You would have to calculate the costs of incarceration; the costs of the family losing its breadwinner and the resulting crimes and poverty that follows; the costs to this country of losing millions of persons that would have voted for the losing presidential candidate in several elections, which would have easily changed the results in several recent elections, and probably would have stopped any war from being declared involving Iraq. Also, think of what millions of persons could have created or work they could have done, instead of languishing in jail (after pleading guilty) because they had no chance of winning the trial against bribed prosecution witnesses and in any event couldn't afford to pay $100,000 or more for an attorney to defend them at trial and pre-trial, and any appeals.
An audit is bound to show that prosecutors as a group commit more crimes than any other group. Society lets them get by with it because as long as it isn't YOU that getting railroaded, you tend to forget about the problem as none of your business. I have talked to hundreds of persons who thought that way one time, before the prosecutor got to their name. There are 5,000,000 or more persons with stories to tell, and another 10,000,000 immediate family members who are suffering from the incarceration of the breadwinner, usually.
Don't get me wrong. There undoubtedly are a substantial number of persons who belong in jail, but society should put them in jail using due process of law and not with bribed testimony, overcharging, inadequate counsel for persons with no money. It is interesting that the persons who do not plead guilty are, by and large, the defendants with hundreds of millions of dollars, more than enough to buy ten great lawyers. And guess what? With all that money, they still wind up being found guilty, except for movie stars. Juries all over the country tend to let movie stars do whatever they want to do, but multi-millionaires are given no break by juries.