Great question on my little Skribit device:
What determines who gets an ADA job -- highest civil service or bar exam scores? Or is it political?
The thing I love the most about this question is its underlying assumption: that an ADA job is a desirable one.
And I love that so much because, in my view, it's absolutely true. Best job I ever had.
But to answer your question, the hiring process is pretty much like other jobs: a vacancy arises, people apply, some get interviewed, and the lucky winners get hired. I believe we have a hiring committee, but I think the final decision is always down to the elected DA.
What does she base her decision on? Hard for me to say. I'm pretty sure it's not based on bar exam scores, simply because no one hires based on those. There's also no civil service exam (was my anonymous questioner from Canada or the UK?!). As for whether it's political, I think not. I say that because my politics were not inquired into, nor did I overtly campaign for either of the DAs that hired me.
And my own experience is most of what I have to go on. The one question I got, over and over in my interview, was whether I wanted to be in court a lot. Some people like the idea of it, but not the practice. And, of course, some people become lawyers and never want to set foot in a courtroom. I assured those interviewing me that being in trial was the reason I became a lawyer, and that I absolutely wanted to spend time in the courtroom. I guess I convinced them because they gave me the job.
Now, my own hiring was a little unusual because my previous experience was all at a civil firm. That means the hiring committee could be assured I had good research and writing skills, but not any experience in trial. That meant sticking me in a courtroom was a bit of a gamble (one I'm very glad they made).
The hiring procedure I usually see is lawyers starting off at the county attorney's office, where they handle misdemeanors, and then, after a few years, graduate over here to try felony cases.
The one thing I've never seen is a brand new lawyer get hired at the DA's office. The reason being that there are many applicants for each spot so there's no real reason to take on someone who's new to practice. They might be good, sure, and very smart. But so are those wanting to work here who already have experience.
I hope that's answered the question fully, if not please follow up in the comments, I'll be glad to elaborate.