'How would you define an "accidental" sin?'
I could give an example here, I used to place Lotto and football pools on for someone every week when I worked in a Nursing Home, as they were a resident they asked me too, well I did this for a few weeks until the Holy Spirit convicted me of it, and brought it to my knowledge that it might as well be me doing them, even though I was the messenger, what sort of message was I giving others?
This was 'accidental' sin on my part.
I had to tell the resident that I could no longer do this, as it was wrong for me to do so being a Christian, the man was an Orthodox Jew, and he fully understood, and apologised.
Another incident of 'accidental' sin as I think, was another resident asked me to go to the off licience and buy her a bottle of whiskey, which I also did, until again, convicted of it, to which I stopped immediatly doing, and took her in my car to the shops and she went to the off licience herself.
I think these speak of 'accidental' sin, as I really was unaware that I was comminting sin.