Many people claim that the argument that a person is Innocent Until Proven Guilty is argumentum ad ignorantiam.  A person who is presumed innocent may indeed end up guilty after the evidence shows them guilty beyond any reasonable doubt, but I disagree this proves Innocent Until Proven Guilty is argumentum ad ignorantiam.
The main principle of argumentum ad ignorantiam is when a person uses a negative claim for evidence as support of a positive claim. To argue a person is innocent because they have not been proven guilty is not evidence of innocence; just as well, to argue a person is guilty because they have not been proven innocent is not evidence of guilt. The previous two arguments claim the other side has not been supported (negative claim), so the opposite is true (positive claim).
Innocence is the term used before the evidence is viewed. I think it is misleading for two reasons: (1) a person cannot know guilt unless they see evidence that proves guilt, and (2) there is a difference between legal innocence and actual innocence. Because of this, the term innocence takes on different meanings based upon the context it is used.
Innocence before the evidence is viewed means a person is charged with a crime, but the charges have not been supported by evidence in front of those who will make a consensual judgment of the evidence.
Innocence after viewing the evidence means the evidence doesn’t support the charge.
Actual innocence means the person really didn’t do it, even if the criteria for evidence creates a circumstance where guilt is found.
Due to the ambiguity of the term innocence one may get confused with its intended meaning in multiple contexts. It is not argumentum ad ignorantiam, because what is meant by the term is to say a person has been charged and the charges will be attempted to be supported by evidence. That is all that can be said in a positive sense, because making a legal or actual claim of innocence would be argumentum ad ignorantiam.
What is your view on the argument that Innocent Until Proven Guilty is argumentum ad ignorantiam?