after a deadly accident where the PIC was not 100% clear, Germany changed it's laws, as mentioned before. Still this subject gets discussed constantly.
Basically, PIC is the pilot flying in the seat that the plane manual declares as the seat for flying solo. If that is not defined, then PIC is the LHS in most planes, RHS for helicopters, front seat for most gliders (as I said, plane manual determines otherwise). The exception is of course training flights where the instructor in the RHS is then PIC.