Dreaming that you are an accomplice to a crime can mean that you feel that you have been placed in a difficult situation that you cannot control.
Being an accomplice to a crime in a dream can mean that you wish to deny responsibility for your actions.
The nature of the crime committed can be important.
Dreaming that you are an accomplice to a violent crime can be a way for you to release anger unconsciously without having to take responsibility for it.
If you dream that you are an accomplice to a theft, you may not want to admit your need or desire for material things. Who is the person in the dream who commits the crime? That person could be an aspect of your personality.
The criminal in your dream could represent a part of yourself that you think is bad or that you feel needs to be kept under control.
By making you the accomplice in the dream, your unconscious allows you to observe and try to understand this part of yourself while still keeping it separate from the parts of yourself that you already understand and accept.