Not much is known about Joe Chill's past.
Joe Chill was created by Bob Kane, Bill Finger and Gardner Fox.
Golden Age / Earth-Two
When The Wayne's left the cinema after a performance of The Mark Of Zorro, they took a route that lead them into Crime Alley where a man was waiting. A man like any other in Gotham City at that time. Except this man needed money, and badly. This man had frightened, hollow eyes and a voice like glass being crushed. He held the Wayne's at gunpoint, and robbed them. Not satisfied with this, he shot them both. Their young son wept beside their bodies. Joe prepared to finish off the remaining family member.
However when he cocked the hammer, the boy looked at him with such conviction, such malice, it was as if the boy's very glance could stop time. Frozen in fear, Chill dropped the gun, and ran away as quick as he could. He came to realize in all his sleepless nights, that he had in fact killed three members of the Wayne family that night. For the boy crying by his mothers side only moments before was not the same as the one who cut a hole in him with his unforgiving gaze. That night he had killed Bruce Wayne, and created the heroic Batman.
Silver Age / Earth-One
Batman discovered that Joe Chill, a small-time crime boss he was investigating, was none other than the man who killed his parents. Batman confronted him and revealed his secret identity ("I'm the son of the man you murdered, I'm Bruce Wayne!") and Chill, frightened, sought protection from his henchmen. Once his henchmen (who had friends that were arrested by Batman) learned that Chill's actions lead to Batman's existence, they turned on their boss and killed him, never giving Chill a chance to reveal Batman's identity.
Batman learned that Chill was not a robber, but actually a hitman who had murdered the Wayne's on orders from a Mafia boss named Lew Moxon. In a flashback, we learn that Bruce's father, Thomas Wayne, had worn a bat-costume to a costume party, where Moxon and his men had shown up and forced him to remove a slug from his arm. Afterwards, he testified against Moxon in court. The crime boss swore revenge, and hired Chill soon after. Batman confronted him years later while wearing his father's costume (since his current one was ripped in his last battle). Moxon, who had amnesia and so did not remember ordering the hit, suddenly remembered what he had done. Thinking Batman was actually Thomas Wayne's ghost, Moxon panicked and ran out into the street, where he was hit by a truck and killed.
Modern Age / New Earth
Several Gotham City crime bosses pooled their resources to deal with a vigilante called the Reaper, and Chill was hired to take him out. When Batman proposed an alliance it was agreed that he and Chill would work together - something Batman found repugnant, but which he nevertheless justified to himself as necessary to tackle the Reaper. He vowed to kill Chill afterwards. Chill was also commissioned to kill Batman after the Reaper had been disposed of. During a major confrontation, the crime bosses were all killed in a battle at a warehouse, in which the Reaper seemingly also perished.
Chill reasoned that he now no longer needed to fulfill his contract, but Batman took him to "Crime Alley", the scene of his parents' murder. There he confronted Chill and revealed his identity. Batman had Chill at gunpoint, but the Reaper appeared and gunned Chill down, leaving it ambiguous as to whether or not Batman would have actually pulled the trigger.
Zero Hour / New Earth
After Zero Hour, DC Comics stated that Batman did not know who had murdered his parents after having seen in an alternate time-line that Chill hadn't done it after all. The rationale for this change was that it would allow Batman to view all criminals as surrogates for the man who killed his parents.
Infinite Crisis / New Earth
During the Infinite Crisis, another cosmic crisis changed continuity, reestablishing that Chill murdered Thomas and Martha Wayne and adding for the first time that he had been arrested for their murder. This change is consistent with the previous year's film Batman Begins, in which Chill was also caught after murdering the Wayne's.
Post-Infinite Crisis / New Earth
When Batman found out whom had murdered his parents, he was led to Joe Chill. Joe was old (late 50's early 60's) and was paranoid by Batman. Batman would constantly stalk Joe for days and even weeks. Destroying his shipments of drugs, weapons and other shipments. Eventually, Batman got the nerve to go to his headquarters/house. Joe had all of his guards ready for Batman, and he wanted Batman's head mounted on his wall. Joe was talking about that he should've killed Bruce Wayne, but he stated that he wouldn't kill young Bruce because he reminded Joe of his son. Joe was also sick, he was extremely paranoid and had to take pills to keep his heart in control.
Batman easily took out all of the henchman, and when Joe saw Batman he peed himself. Batman gave Joe the gun that killed Bruce's parents, and Batman stated that it only had one bullet left. Joe figured out that Batman was Bruce Wayne, and knew that if he told anyone they would kill Joe. Joe went to conclusion that he should kill himself, and went through with it. Batman stood on his rooftop grinning. This was eventually found out to be a flashback that Batman had when psycho ex-cop/Batman Lane stopped Bruce's heart then started it back up again. The Joe Chill flashback was when Bruce Wayne started his beginning days as Batman!
The New 52 / Prime Earth
In the New 52, and with it certain character's origins changed. Joe Chill, had still shot Thomas and Martha Wayne, but only because Martha screamed and startled him. Joe escaped, only to learn who he killed the next day. Bruce becomes determined to find out who killed his parents, scouring Gotham's slums for answers until he was pointed to a homeless ex thug. The thug wouldn't give up information willingly and demanded something in return. Bruce reluctantly gave him his fathers watch.
The thug says all he knows is a name: Joe Chill. Bruce becomes obsessed, believing Chill had to be working for as a hitman, or a mafia, or even part of a massive conspiracy (Even digging into the Court of Owls). Bruce eventually finds where Chill lives, but first returns to the homeless thugs and takes his fathers watch back. Bruce bursts in, ready to kill Chill, only to find him in an almost empty, dirty apartment. He was just a simple man trying to make a living. No conspiracies, not gang leaders. Realizing he was just a homeless man trying to live happily, Bruce leaves him.
Major Story Arcs
Modern Age / New Earth:
The New Reaper
Chill's son (also named Joe Chill) appeared, taking on the identity of the now deceased Reaper. He sought revenge for his father's death, and subsequently attempted to drive Batman insane by using hallucinogenic drugs to trigger Batman's survivor's guilt over his parents' deaths. Chill knew that his father had killed Batman's parents, but did not know of Batman's identity. However, thanks to the intervention of Robin, Batman was able to free himself from the drug-induced haze, and overcome his guilt. After the new Reaper was defeated, Batman accepted that the bad blood between him and the Chills was now over.
Post-Infinite Crisis / New Earth:
The Death of Joe Chill
Chill cut a deal with the Gotham City District Attorney to give evidence on Carmine "The Roman" Falcone, whom he shared a cell with in Blackgate penitentiary. As he left the court a free man, he was murdered by a killer for hire before he could give states evidence against Falcone.
Powers and Abilities
Joe Chill has no powers.
Joe Chill carries a hand gun.
What Ever Happened to the Caped Crusader?
In the events of Neil Gaiman's What Ever Happened to the Caped Crusader? story arc Joe Chill is the bartender at a hole-in-the-wall bar in Crime Alley. He greets Selina Kyle as she comes in for Batman's Funeral. She recognizes him and inquires that she thought he was dead. He replies "I was here at the start of it Miss Kyle. I'm not going to miss the end."
In the Batman daily newspaper comic strips later reprinted in the Batman: The Silver Age Newspaper Comics #3 - Volume Three: 1969-1972 It was revealed that Joe Chill had a son named Michael Chill. Michael after learning from a scrapbook dedicated to Bruce Wayne created by Mrs. Chilton that Bruce Wayne was Batman. Learning that his father was killed by the Batman looked to get revenge on the Batman.
The Super Powers Team: Galactic Guardians
The episode "The Fear" a flashback depicts Thomas and Martha Wayne being mugged by Joe Chill.
Batman: The Brave and the Bold
Chill has a large role in the episode "Chill of the Night" in which Batman finally finds out that Chill is his parents killer. After Lew Moxon dies he reveals he hired Chill to off the Waynes. In the present day Chill is a weapons dealer selling weapons to various Batman rouges. Batman confronts him, but decides not to kill him. The Spectre however, brings about building to collapse on him in revenge.
Justice League Unlimited
The JLU episode "For the Man Who Has Everything" features an appearance by Joe Chill. In the sequence, Bruce Wayne has a hallucination in which his father is not shot, but instead disarms Chill and starts punching him, much to young Bruce's delight, until Chill gains the upper hand and ultimately shoots and kills Thomas and Martha. The scene is reimagined when Batman is captured by the "Black Mercy" plant, an alien plant which traps its prey in the fantasy of their heart's desire.
Unlike Superman, who created an entire new life while he was under the Mercy's influence, Batman's fantasy never leaves from his father beating Chill continuously. Only when Wonder Woman tears the Mercy off him does the story return to its historic pattern. In an ironic twist of casting, Chill's is voiced by Kevn Conroy , the voice of Batman in the DC animated universe.
Batman Begins (2005)
In the Nolan Series, Chill Appears in the film quite prominently. In the mugging flashback he is depicted as desperate (due to Gotham's recession) and quite cowardly. Years later he is in court after promising to give evidence on Falcone whom he shared a cell with. Falcone's men shoot Chill before he can talk, right before Bruce was able to get revenge himself. He is played by Richard Blake.