This is an entirely theoretical question, but I am not sure how it is explained.
Consider someone committed a crime, but due to lack of evidence the charges are dropped. A lot of people would say they are innocent, but that is not the case as they did commit the crime. But they were also not found guilty due to lack of evidence. They they are basically in no where land in the middle.
How is that explained legally?
Scotland has a third possible verdict, which covers much of the situation you are asking about: “not proven”. While still an acquittal, it is typically used by judges and juries in situations where they are not suitably convinced the defendant is necessarily innocent, but not convinced the evidence supports a conviction.
As recently as 2015, attempts to remove the third verdict from the Scottish legal system were rejected, despite it being seen as an easy way out for courts.
Your question assumes the omniscient-observer perspective, that there is someone who knows everything but doesn't interfere in human affairs. Thus the premise; the person committed the crime, nobody knows this, at most one can only speculate whether it's possible.
We have no access to this absolute source of knowledge. The legal system is based on what we do know. With a little bit of knowledge, the police might interrogate the suspect; with more evidence they might arrest him; and so on to a trial, and a conviction (strongest evidence), deadlock (i.e. hung jury – weaker evidence) or acquittal (even weaker evidence).
All told, there are many degrees of proof that the accused committed the crime, where the legal system requires a certain degree of evidence that it is true that he did it for each infringement of the suspect's rights.
The legal system can only deal in the relationship between evidence and the accusation – it can't appeal to a higher omniscient power to distinguish between "provable guilt" and "actual guilt".
When the jury decides on a verdict of "guilt", that means that the evidence that against the accused is so strong that it is unreasonable to believe that he did not commit the crime. It is generally sufficient to limit the question to asking whether it is proven that he did it (guilty) – otherwise he is not guilty.
You can add other categories, and Scotland does, but the legal question is "Is it proven that they did it", which only has two logical answers, "yes" or "no".
It makes a different whether "charges are dropped" or whether there is an actual trial and the person has been acquitted. It also makes a difference under what jurisdiction this occurs.
In most US jurisdictions, when charges are dropped, it means that the investigating authority (police, normally), or the prosecuting authority (DA, PA, or US Attorney), or possibly a Judge at a probable cause review have not found sufficient evidence to proceed, or perhaps simply do not think it is worth the time and trouble to proceed. But this is not a final decision. If additional evidence should come to light, charges may be reinstated.
However, when a person is acquitted, that is normally a final determination, and the Double Jeopardy Rule will prevent further proceedings in the matter (except in cases where an act is both a state and a federal crime).
When a person has been acquitted, it may be said that that person has been found not guilty. It might also be said that in a legal sense that person is not guilty, that is the person can never be found guilty by the legal system. That the person actually did the crime, if that is true, is in a legal sense irrelevant.
I think that similar rules will apply in many countries, particularly common-law countries, but I am not sure about that.
The question "how is this explained legally" is worth answering.
Its not the same as "how does guilty/not guilty work", or even the "not proven" verdict in Scottish law.
The idea here is that a prosecution pits an Individual against the full power of the State. A state can easily abuse that power, and many states routinely do so today. Most of the rest, even if they do mostly follow rule of law now, did in the past, and can at times abuse at present.
For example, if there were no rules, we might be less sure evidence was reliable. A person accused, or even found innocent, could be constantly at fear of a second, third, or tenth inquiry/prosecution. Obviously the state doesn't live in fear for years or ever, but individuals can and do.
So in criminal law theory, a number of rules exist that specifically address this imbalance and aim to reduce the incentive for abusing power. Some of those rules are behind the answers to your question.
A main idea in UK/US law, is that the state, with all its power, gets just "one bite at the cherry". If they think a person did something, they have to prove it, and if they can't totally convince a jury then they don't (usually) get a second chance.
That's the idea behind so called "double jeopardy" laws, that generally you can't be tried again for a crime if acquitted. The state can wait and avoid a case until they are sure they have enough to prove it, but they need to be sure they have that strong a case, because they won't get a second chance if they fail. You can see how that can work as an incentive for careful work, as well as preventing many kinds of abuse.
A second idea is that a person is usually considered innocent unless and until proven guilty. That means, if the state, with all its power, could not totally convince a jury they did the stated crime, then the public at large should not assume they did it, either. Even if they did do it, if the state couldn't convince a jury then that is a big red flag that society at large shouldn't assume they did.
Being accused as a criminal is a heavy burden, for life, so if it isn't clear, its usually seen as better to play safe and not ruin someone's life, even if there is a chance they did it.
In a realistic view of the world, there is always a chance that some will be punished who didn't do a crime, or some will be let off who did do one. You don't get to avoid these, because you dont have perfect knowledge. You only get to choose which kind of error is more important to try and minimise.
As someone that has served on a criminal jury at a criminal trial, I can say that the verdicts "guilty" and "not guilty" don't literally mean that.
The jury isn't actually judging the person, but the evidence against that person:
Every member of the jury may very well personally believe that the defendant did in fact commit the crime, but still return a verdict of "not guilty".
The verdicts "guilty" and "not guilty" are really short for "proven guilty" and "not proven guilty".
There is no "innocent" verdict.
You yourself use “guilty,” “not guilty,” and “innocent”—don’t these three things already provide for exactly the distinction you are looking for? Also note that defendants aren’t asked if they’re innocent, and are not required to prove they are innocent, and the verdict that a jury renders doesn’t say they are innocent—it says they are not guilty.
“Not guilty” means exactly that—that whatever standards are in force to define what it means to be “guilty” of a crime have not been met. Those standards include the existence of a certain amount of evidence of the defendant’s guilt. If the evidence isn’t there, then the case doesn’t meet the standards for a “guilty” verdict, and so the defendant is not “guilty,” that is, they are in fact “not guilty.”
But nobody said they were necessarily “innocent.” That wasn’t the court’s job to determine, and they haven’t made any significant attempt to do so, so they do not render any judgment on that question. In fact, the courts are explicitly required to ignore that question—instead, they have to treat everyone as “innocent until proven guilty.” Legally, we assume that the defendant is “innocent until proven guilty,” that is, “not guilty” is the same (legally) as “innocent,” but “innocent until proven guilty” is not an actual claim about the person’s “actual” innocence. Instead, it is explicitly an assumption made in recognition of the court’s limitations, both in terms of what they’re capable of demonstrating, based on the investigation that was performed and the case that was made, as well as in terms of the limitations on the court and law enforcement as a whole that were put in place to protect everyone’s rights.
So, in short, the court can only distinguish between “guilty” and “not guilty”—“innocent” is a third state that isn’t the court’s job to determine. In lieu of determining innocence, courts treat “not guilty” (as well as those whose verdict has not yet been determined) the same as “innocent,” but it doesn’t mean that they are claiming the person actually is innocent—they’re simply required to treat the person that way because innocence isn’t their business and treating everyone that way protects everyone’s rights.
In england-and-wales a person is only guilty of a criminal offence when they have been found guilty by the court after a trial that considers the evidence for or against the defendant (or following the defendant's guilty plea).
In other words, how do you know they actually committed a crime without looking at all the facts - was it murder or self defence? Theft or reasonable excuse? Assault or mistaken identity?
Like most jurisdictions, this is based on the legal principle of presumed innocent until proven guilty.
You are missing a 2nd "middle ground".
Blackstone's ratio is the idea that It is better that ten guilty persons escape than that one innocent suffer.
This legal principle is somewhat common across many legal jurisdictions, and it attempts to prevent a miscarriage of justice, where someone who did not commit the crime is found to be guilty. This is the second "middle ground".
The opposite to that is known, at least in some publications as, errors of impunity, where someone who did in fact commit the crime was found to be not guilty. This is your "middle ground".
The facts of the matter, and the courts finding on the matter, don't have to agree. The above terms are exist because of that reason.
The word "guilty" has multiple different meanings.
In one meaning, a person is guilty if they have committed a crime. The mere action of committing the crime automatically makes the person guilty.
In another meaning, a person is guilty if they have been convicted of a crime. Initially, defendants are not guilty, but if a jury finds them to be guilty, they become guilty at that moment.
As you've noticed, it's possible for a person to be guilty in the first sense, but not guilty in the second sense. (The reverse is also possible, of course.)
First of all, "guilty" and "not guilty" are not the only two possibilities in most of the world. Here are some others:
If the charges are dropped voluntarily then Nolle prosequi seems to be the most appropriate term to use.
Technically the terms "guilty" and "not guilty" are "not applicable" if there's no charges, and I highly recommend this answer by user6726 which comments on the fact that legal systems around the world usually are based on what we are able to know (evidence) rather than appealing to some "higher omniscient power" that can distinguish between "provable guilt" and "actual guilt".
If you insist on labeling the defendant as "guilty" or "not guilty" with no other options, it would (legally) be more correct to label them as "not guilty" than "guilty" because they have not plead or been found "guilty" if you are using the word "guilty" as the legal word. You are also free to use the word "guilty" in your own colloquial sense too (for example to mean "I know she committed the crime, even though no one saw it"), but others may disagree with your use of the word in this way.
The "Presumption of Innocence" comes from Blackstone's Ratio which holds that:
It is better that ten guilty persons escape than a single innocent man suffers.
The phrase was not original at the time, but Blackstone is the person who in 1760 brought it to the staple status it is in Common Law based legal systems such as those used by the U.S. and U.K. That said similar concepts can be found in Voltaire (1748), Codified in Russian Law (1715), spoken at the Salem Witch Trials (1692) and even found in the Book of Genesis in the Bible (Specifically an exchange between Abraham and God where God tells Abraham of his intent to destroy the cities Sodam and Gomorrah, Abraham brings up despite the wickedness found in both cities, there are righteous people in the city... and then haggles with God over how many righteous people must exist to spare the city, getting the number down to 10, which Abraham does find in Lot's family... and once the wicked residence force Lot and his family to flee in fear of their safety, there's no righteous left to spare the cities from God's Wrath).
At any rate, the ratio holds true that no matter how terrible the actual crime was, society is better off with those who are factually guilty of an accused crime going free if it means that someone who is factually innocent does not suffer punishment at the hands of the government.
If all of the elements of the offense are present, they are guilty of the crime. That a court or proceeding hasn't found them guilty or found them not guilty doesn't change the fact that they are guilty. The word you are looking for is "guilty".
There is a distinction between the truth and our attempts to find the truth. A verdict of guilty or not guilty is a finding. It may or may not be the truth.
It would, of course, be an error to say they were "found guilty" by a court, since they weren't.
