To be a witness while being somewhere else and using technology to testify anyway, is not possible since ‘technology creates a void’. If a witness is elsewhere, the witness has to go to a court where he/she is located to be sworn in and testify over there. Only in such a case a video or phone connection might possibly make sense. In this sense trust is transferable property between trusted places.
Physical presence is necessary, technology creates a void
Physical presence is necessary when assessing the witness contribution to the search of the truth. The physical presence of the witness in court is crucial when taking the oath and testifying.