A criminal most likely represents the bad part of yourself, not necessarily the part of you that would go out and rob a bank but more likely the part of you that would give in to temptation or do something against your own rules, like cheat on your diet for example.

If a crime is committed in your dream, ask yourself if you feel someone has done you wrong in real life, or if you are the one that behaved poorly. What is going on that is rubbing you the wrong way or what have you done that goes against your grain? Your dream is showing it to you in the form of a crime so you can better understand the situation or your behavior and correct it.