If Bruce Wayne could call anyone his best friend, Ethan Bennett is it. They've been friends since high school. Whereas his partner, Detective Ellen Yin, sees things in black and white, Ethan sees the grey in almost everything – and is more willing to allow The Batman to co-exist with the Gotham P.D. After being subjected to a gas from The Joker, Ethan was left physically altered - becoming The Clayface. Bennet became more and more corrupted by his power, making him one of Batman's most unpredictable and tragic adversaries, though he did show remorse and was cured of his condition in Clayfaces.

It was implied he becomes Police Chief in the near future during the fourth season episode "Artifacts." He is voiced by Steve Harris.

Info from Wikipedia