Chas first appeared in Hellblazer #1(Jan 1988), created by writer Jamie Delano with artist John Ridgway.
The Pair's friendship can be traced back all the way to the late sixties, when a young adolescent 16 year old John Constantine was spat onto the streets of London for the second time in his young life with nothing to his name but a pack of silk cut cigarettes and an overly sly and sarcastic sense of humor. When he found no success , he found himself eager and desperate to put a roof over his head, John immediately leapt at the chance to move in with his new-found friend (Chas).
Chas eventually became one of John's oldest and closest friends with their relationship of pulling each others ass out of tight situations, with Chas providing the brawn and Constantine, of course, the brains.
Chas is married to Renee, who unfortunately spends the bulk of her time ragging on Chas, usually about some problem which roots back to Constantine, a man which Renee has come to dislike strongly.
When Chas was possessed by Nergal and later released, enough of Nergal's taint remained to leave Chas completely uninhibited; Chas went on to have sex with an underaged hooker and beat Renee severely.
The pair have one daughter, by the name of Geraldine, who is an adult with a child of her own named Trish.
Chas eventually went on to become a taxi driver, a profession found convenient for his ever-trouble-causing friend. John always seems to use Chas as his "wheels" to transport him anywhere he is needed, whether Chas knows what is going on or not.
John often tries to keep Chas protected from the dirtier aspects of and characters in Constantine's life, for his own good. Both John and Chas often happen to part on bad terms, but one quick pint and another adventure later, and the friendship is back together as quick as it ended.
Chas made a brief appearance in the mini series Brightest Day Aftermath: The Search for Swamp Thing, making it his first appearance in the mainstream DC Universe outside of Hellblazer.
He also appears in the video-game tie-in comic Injustice: Year Three where his name is spelled "Chaz".
A version of Chas (given the last name "Kramer") appears in the 2005 Constantine film, played by Shia Lebeouf. Here he is portrayed as a youthful sidekick and driver of a stolen taxi cab, enthusiastic to learn about the occult but often pushed aside by John. Although he dies during the films climax, he appears as an angel in a post credit scene.
Charles Halford portrays an American version of Chas in a series regular role for the NBC TV series Constantine. Described as John's longest known, and longest surviving friend, he makes his debut in the pilot episode "No Est Asylum". Unlike the comics, Chas' knack for surviving has have a supernatural explanation.
He drives a taxi cab, which bares the logo "Yellow Crown Cab Co". This is a reference to a role played by Halford on the show True Detective called the "Yellow King".
Chas' supernatural ability to survive death was explained in episode 10 "Quid Pro Quo" , which also included plot elements based loosely on the story from Hellblazer: All His Engines and introduced his ex-wife and daughter. While in a club together, John had drunkenly placed a protection spell of Chas. When the club caught fire, Chas was burned and killed along with 47 others, but survived due to John's spell as he learned he had absorbed the lives of the 47 others into his own body.