I was driving N/B 101 freeway w my wife at approx 70 mph. I felt the rear end slip ever so slightly and thought maybe I somehow lost traction w the road. I continued driving and it occurred twice more in the span of a few miles. I then realized it was unlikely I continued to lose traction with the road. I told my wife something felt wrong and began to maneuver from the #1 lane to the shoulder. I slowed to 50 mph and continued straight w my foot off the accelerator and the brake with both hands on the steering wheel in a straight (non turning) position. Suddenly, the rear end of the vehicle came out and we went into a massive spin. It ultimately caused us to crash into a median wall. I have been through many driver's courses. I have been through many skid pad trainings. I have also been through Precision Intervention Technique (PIT) training. I have been in both the receiving end of a PIT and the giving end of a PIT. The force of this spin was greater than any spin I have felt. It felt like one side or perhaps both rear wheels locked up. I have no other explanation that could cause any vehicle to just spin out of control while driving straight at 50 mph.