I'm not an attorney, but, did some contract work for a Criminal Defense/Civil Rights attorney. Dennis' comments pretty much nailed it. I want to recommend that you start out working in prosecutions (District Attorney's office) for a couple of years. Why? So you can learn the in's and out's of how they operate! A lot of criminal defense attorneys start out that way.
Making a "deal" on behalf of the client sometimes has further consequences, esp. if the client is not a US citizen, or, is looking to bring a Civil Rights case against the arresting officer. It's important that you understand these consequences.
Wishing you the best!