While the rule for all carriers is that ticket must be used in sequence, otherwise the ticket will be cancelled, but there are exceptions. Last year, one of my friend had a trip on UA from CHO to PVG connecting in IAD and SFO. It was winter time, so the weather was very bad. It snowed heavily on the day before her flight, and because the CHO-IAD leg was on a saab 340 regional, she was frightened that if the CHO-IAD flight went wrong it could bust her whole trip. So she decided to have me drive her to IAD the night before, and stays at Marriott for one night. When she went check-in in the morning, the agent told her reservation was suspended due to the no-show condition of the flight led. She then explained to the agent, and the agent was very nice, and got her reservation re-confirmed.

So I say there will be exceptions regarding this issue, but I don't recommend you to try. Since you will be in trouble if being denied boarding.