The cult of Murphy
One interesting dimension of the film is that it implies that Murphy has a cult following among criminals. Because Elvis was his father, it seems to have made him some kind of criminal royalty.
You can see it when he calls the guy to bail him out of jail. Murphy never implies that he will pay the guy back, but he fully expects him to bail him out immediately, no questions asked.
You can also see it at the end when the same guy asks, "Is he really your father?" That guy was willing to die for Murphy because of an almost cultic attachment to Murphy as Elvis' son. His dying wish was simply to know for sure that he had been with Elvis' son.