Christie was the head of "human interface" at Apple. His team designs software for Apple devices and reported to Apple's sotware head, Craig Federighi. Following Christie's departure, the team will report to Senior VP Jony Ive. The latter has become more involved with the design of Apple's software following the departure of Scott Forstall in 2012. Forstall left after the launch of Apple Maps revealed that the application had been released too early, and was not ready for prime time. Ive took over the design of iOS 7, replacing the vibrant colors with pastels, and removing the skeuomorphic designs that were so favored by Forstall and Steve Jobs.
Christie spent 18 years at Apple, including 2 and a half years working daily on the OG Apple iPhone. His departure allows Ive to consolidate his power over design at Apple. Recently though, he and Ive have not seen eye-to-eye on certain software decisions. Some believe that Christie's exit was due to his disagreements with the Senior VP.
The departing executive is listed on almost 100 Apple patents, including one received on Tuesday for a way to unlock a touch-screen phone. He also has 31 patent applications pending at the USPTO.