The trouble to the two witness exception of a female raped in a field is negated by Pauls counsel not to accept accusation against an elder unless there are two or three witnesses.
http://biblehub.com/1_timothy/5-19.htm
"Do not listen to an accusation against an elder unless it is confirmed by two or three witnesses." (1 Tim. 5:19, NLT)
But Jackson seems to say that the circumstances are yet another witness. Never heard it put that way before. But this just goes to show how their interpretation can make just about any verse mean whatever they want it to mean.