In the passage of Great Expectations when "Provis" relates his history to Pip, he explains that he grew up in the streets, "Tramping, begging, thieving, working sometimes when I could..." At Epsom races Compeyson took him on as his parnter and had Provis put his evil ideas into play. When they were arrested and put on trial, Compeyson looked the gentleman with his
"curly hair and his black clothes and his white pocket handkercer, and what a common sort of a wretch I looked. When the prosecution opened, I noticed how heavy it all bore on me, and how light on him. When the evidence was giv in the box, I noticed how it was always me that had come for'ard, and could be swore to, how it was always me that the money had been paid to, how it was always me that had seemed to work the thing and get the profit. But when the defense come on, then I see the plan plainer; for, says the counselor for Compeyson, 'My lord and gentlemen, here you have afore you, side by side, two persons as your eyes can separate wide; one well brought up, one ill brought up.'"
The greatest crime of Provis is having been poor. Through this character, Magwitch, whose name suggests "magic witch," Dickens develops his recurrent theme of Society as a Prison as well as the prevalent theme of Appearances vs. Reality. Poor and destitute, the intrinsically good Magwitch has had no choice but to steal if he would eat and survive.
In his Victorian society, with the industrialization of his age, countless poor came to London in search of work. As a consequence, those shut off from the promise of work turned to smuggling, pickpocketing, swindling, and thievery of every kind. Those who were able to escape the crime of the city built up the towns, as does Wemmick in Great Expectations. Having had a father in debtors' prison and having to work as a child, Dickens was extremely sensitive to the conditions of his society, which he perceived as a prison itself that bred criminality. His character Magwitch is such a victim of the prison of society.
Typically, when you think of criminals, you think "bad guys." In Great Expectations, however, it isn't that straightforward. Yes, there are criminals who fit the typical mold; consider the nasty Compeyson, who corrupts Miss Havisham's fiance and fights with Magwitch throughout the entire novel. He is a pretty bad guy who manipulates and connives other people, not caring about the damage that he causes. So, he fits the mold of a "typical criminal" pretty well.
However, Dickens presents Magwitch in a much different light. At the beginning of the novel, and even for most of the novel itself, we think he is a terrifying character who bullied a little boy into helping him to escape. He is uncouth, uneducated, mean, frightening and possibly very dangerous and violent. This is all pretty scary, and as presented through the young Pip's eyes, we see him as a total villian. Dickens, however, doesn't let it rest at that. Come to find out, Magwitch is more of a victim of circumstance, played by the more conniving Compeyson, and fallen onto hard times. He has been used by Compeyson, and been an unfortunate pawn in his criminal strategies. Also, as he is banished and works hard to supply Pip's fortune, we learn that he is a principled, hard worker who wants a better life for someone who was kind to him. Magwitch, it turns out, is generous, gracious, kind and incredibly driven and motived. Those elements do not fit the stereotypical criminal profile. Dickens takes our assumptions of criminals, and says, "Hey--don't judge until you know the entire story." He often does that with characters, not just criminals.
Arthur is another example of someone we boo as a villian, but who is really just a guy who got manipulated into a scheme, and dies haunted by his actions, regretting what he did. He was a willing player at first, but his morals get the better of him. Again, not typical criminal behavior there.
I hope that those thoughts help a bit; good luck!