First of all, some disclosure is in order. I am not a former prosecutor. I have never worked for a prosecuting agency. I've never volunteered at a prosecuting agency. I have never prosecuted another human being. I am a career criminal defense attorney. My entire legal career (all 25 years of it) has been spent defending clients in criminal cases. I didn't necessarily start out with the goal of becoming a criminal defense attorney. It just sort of happened. It only took me a few days, however, of working on the defense side of the criminal justice system to realize that this is where I belonged. This is where the most people needed the most help.
There is nothing inherently wrong with prosecuting. It is a necessary part of our criminal justice system. There are some good, decent, and fair prosecutors. There are also some sleazy, conniving, and evil prosecutors. People who don't care about justice, but only care about getting a conviction no matter the cost.
I find it interesting when I see defense attorneys advertise themselves as former prosecutors. The implication seems to be that these attorneys, because of their former job, have some sort of advantage over everyone else. Perhaps they have an in with the police, or the judge, or the probation department. Perhaps they have more experience due to their years as a prosecutor.
The fact of the matter is ...they don't. The only similarity between prosecuting and defending criminal cases is that they both take place in the same courtroom. Defending a criminal cases is much more difficult than prosecuting one. An entirely different skill set is involved.
When seeking criminal defense representation, the relevant question is not how long the attorney has worked in the criminal justice system, but how long the attorney has worked in criminal defense.
Prosecutorial experience does not count as criminal defense experience. It would be like using a particular heart surgeon because you heard that he used to be a dentist. Apples and oranges.