Am I responsible for an expired registration ticket given to me while I was driving someone else's car.

The code on this charge contains an element of knowledge and service. If you did not know, it may be a defense to the charge. Look at code section O.C.G.A. 40-6-15(a), "Any person who knowingly drives a motor vehicle on any public road or highway of this state at time when the vehicle registration is suspended, canceled or revoked shall be guilty of a misdemeanor." Remember that the State has to prove all of the elements of your case beyond a reasonable doubt. You also have the right to remain silent. If you do not own the car, and the State has no one to testify that you knew that your license is suspended, they may not be able to prove your case.