Harvey Harris was a Gotham City Police Detective that helped to try and stop the KKK in Detective Comics Annual in 1989. He is good in combat and claims to have a black belt. He uses his skills as a detective more than he uses a gun.
The first story told about Harvey was in Detective Comics #226, as seen on the cover, Robin confronting Batman about a reel to real movie of Robin, but Dick Grayson questions the validity of the film, and Batman tells him that it is not him in the movie but him (Batman) before he had the idea of becoming the Batman. The story tells how Batman became Robin first and was tutored by Harvey Harris.
In the Untold legend of the Batman three partner which gives pre-crisis tales of Bruce Wayne‘s early struggles before becoming the Batman; Batman reveals the story of who trained him. He wore a Robin costume to hide his identity and then sought out the assistance of Harvey Haris. Bruce would go on to say that Harris was probably the first person to actually figure out his identity.