Earl, it becomes clear, has had a colourful past, and this is not solely restricted to his relations with the various authorities he has had dealings with. Consider how, at the outset of the story, Earl is looking to leave Montana because of various troubles that are chasing him. These euphemistic "troubles" take the form of a number of bad cheques he has tried to cash that have the potential to get him put in jail because of his previous criminal record.
Although a lot of what he has done in the past is not revealed to us or expounded, it is clear that Earl, throughout his life, has been happy to break the law when it suits him. Not only does the evidence suggested by the bad cheques support this assertion, but also the fact that he leaves Montana in a car that he steals. The cranberry Mercedes that he steals from the lot of an opthamlogist is ironically a car that gets Earl into trouble when it breaks down and triggers an epiphany that causes Earl to take a long hard look at his life and to question what he is doing and where he is going.