 To become a criminal defense lawyer, a person will typically complete their undergraduate degree, and then attend and graduate from a law school.After graduating law school and passing the bar examination for that particular state or jurisdiction, the new lawyer will be sworn in as a member of that bar and can then begin practicing in the field of criminal law.However, many reputable criminal defense attorneys spend some time after being admitted to the bar working under the mentor-ship of an experienced attorney, often in a prosecutors office or a public defenders office.