I excerpted enough for you to understand (I hope).
'Amendment VI
In all criminal prosecutions,'
If jail is a possible punishment, then it’s a criminal prosecution, no matter what the courts try to label it to get around the constitution.
Maybe this will illustrate my point better, from Black’s Law Dictionary:
“In contradistinction to criminal, it indicates the private rights and remedies of men, as members of the community, in contrast to those which are public and relate to the government ; thus, we speak of civil process and criminal process, civil jurisdiction and criminal jurisdiction.”
Law Dictionary: What is CIVIL? definition of CIVIL (Black’s Law Dictionary) http://thelawdictionary.org/civil/
Imprisonment is not a “private remedy” available to members of the public. It is a distinctly public remedy that can only be imposed by the government. Therefore, any prosecution that carries a possible term of imprisonment is by definition a criminal prosecution.