Clearly Wrong = physical evidence or scars.
In a family context, I say it's simple, the line should be be clearly defined and drawn by how the child feels toward the person delivering discipline. Is it fear or terror? Parent or mob leader. Definition should be determined by the consequence of the relationship between the two - child and parent.
Therein lies the problem. What this means is that the child has to be involved in the process for it to be proven. The system discourages it, of course so would any parent. But what is the end result - a hope stage that the abusive party will undergo counseling and change.
So if there is no change on the part of the abuser, the next step will involve the children won't it? Hindsight is now experience. There is no point going through the 'vague' system. Get a mouthpiece (lawyer) who will go through all the facts and interpret it as it should have been in the first place.