John Decker was born in 1956, and was raised in Los Angeles. At some point, he became a police officer with the LAPD after graduating from the LAPD Police Academy in 1977. He married Penelope, who was a famous 80's sci-fi movie star. At some point, they struggled to conceive, Amenediel was sent incognito to bless them, and later they had a daughter, Chloe in 1981.
John Decker was murdered in June 27, 2000. John's murder was actually not a robbery but an intentional assassination. His murder had been orchestrated by a corrupt prison warden named Perry Smith. Smith also arranged for Joe Fields, an innocent man, to take the fall for the murder in return for money. Because of Penelope's fame, paparazzi invaded his funeral and Chloe ended up punching Nick Hofmeister's camera. Shortly after, Chloe left acting and decided to join the LAPD. Sixteen years later, Chloe arrested Perry Smith after finding proof that Fields could not have committed the crime. However, with Goddess's help (while posing as the human attorney Charlotte Richards), Smith got acquitted. Later, Dan and Maze inform the Russian mob that Smith was responsible for Boris Sokolov's murder and where to find him. The mob kidnap and murder Smith.
In creating an alternate universe, God saved Decker's life by moving the bullet a few inches to the right. Eventually, Decker became a detective, holding the rank of lieutenant while Chloe stayed an actor.
After Chloe is killed by Michael, she is reunited with her father in Heaven. When Lucifer arrives to resurrect her, Chloe is torn between returning to Earth and staying with her father. Proudly addressing Chloe as Detective Decker, John orders his daughter to go back to the people who need her, promising to be waiting for Chloe in Heaven when she does return. Sadly, due to the fact that Chloe did not stay in heaven after her death but went to hell to be Lucifer's eternal partner, he never saw his daughter again.
John's death was the essential moment that shaped Lucifer and Chloe coming together and Lucifer becoming police consultant. In "Once Upon a Time", God revealed John's death set about a chain of good events in the lives of those close to Chloe.