Barnaby holds a golf club with a rubber handle to the electrified items and an arc results. If the handle was rubber then no current would flow and no arc would be generated.
At around 35:20, Barnaby digs out a handkerchief with which to pick up a piece of evidence; despite this, he clearly holds the evidence with his bare fingers, including his little finger flush on it and square to the camera for a number of seconds.
No explanation is ever given for the murdered second body found in the crop circle.