DO seek out a lawyer that only handles criminal defence. You do not want to find someone who has only handled a couple of cases of this specialty. This means that you will be at the mercy of someone who is not really aware of what they are doing. Ideally, your lawyer should have been working in this arena for 10-15 years before you hired them. You can read more about the process of searching for criminal defence specialists on this page.
You should also be careful of people who used to work for the prosecution. There are some lawyers who were once on the opposite side of the fence and have decided to make a career change.