Grand Juries have a very high indict rate, especially federal ones, but there’s arguments about why that is.
One argument is obviously that grand juries are pushovers and indeed would literally indict a ham sandwich.
The other argument, hinted above, is that prosecutors only move to indict if they think they have a chance to win at trial. Since the evidentiary standards are much higher for conviction, that means they easily clear the requirements for the grand jury indictment the vast majority of the time.
It's not just that they're pushovers, it's a completely one-sided affair. They only hear from the prosecution (the defendant is not present, let alone granted legal representation) and the prosecution is allowed extensive leeway in attempting to gain the indictment including offering evidence that would not be allowed in trial, such as hearsay [1]. And whether a case can be won or not at trial is a secondary consideration for prosecutors. The vast majority of cases end up finishing in plea deals out of court. Above somebody mentioned 3%. The exact number will vary by state, but is invariably well below 10%.
So more important than whether a case can be won at trial is whether or not a defendant can be pressured into conceding. And in many things it's generally not hard. Imagine you think you have an 80% chance of acquittal at court, which would see you set free immediately. Yet losing at court would see you serve up to 10 years. And the prosecutor offers you 2 years + time served, which with early release means you'll be spending about a month in jail. Even though you are innocent and think there's an overwhelmingly good chance of being able to prove as such, you'd be a fool to do anything except accept the plea.
In some ways I wish plea bargains were not a thing. It'd massively reduce our arrest and imprisonment rate simply because we could not fulfill the constitutional requirement of a speedy trial with millions of people in the system for mostly irrelevant crimes, and it would also avoid this sort of 'loophole' of allowing prosecutors to score convictions even when the defendant felt he would have a good chance of defending himself at trial but is unable to do so due to risk:reward considerations.
If you want to reduce the rate of arrests in the United States, we need to change the culture around the fetishization of punishment. The belief that those in jail "deserve" everything they get, including inhumane treatment, drives all that is ill with our criminal justice system. Adjusting how plea bargains work might help and might not, but we need to start changing culture first.
Having been through the federal criminal system, I can vouch the sentence one can receive after loosing a trial can be ten times longer than one plea bargained for.
I also read in the DOJ report that they dismiss not so significant number of cases for the lack of overwhelming evidence or for the lack of criminal intent.
Yes, that is also true. One must always keep in mind the opportunity cost of prosecution, where losing a case means that you might have one a different one with the same resources.
One argument is obviously that grand juries are pushovers and indeed would literally indict a ham sandwich.
The other argument, hinted above, is that prosecutors only move to indict if they think they have a chance to win at trial. Since the evidentiary standards are much higher for conviction, that means they easily clear the requirements for the grand jury indictment the vast majority of the time.