<p>This is, of necessity, a simplified answer. The US has state and federal courts. State crimes--including murder--are prosecuted in state court. Federal crimes--such as securities fraud--are prosecuted in federal courts. </p>
<p>Many attorneys become ADAs after doing clinical work in law school with a district attorney's office. It's not essesntial, but it's a good way to get an "in." So, the kid of one of my colleagues went to a local law school here in NYC--which is NOT T14--and did an internship for credit with one of the county DA's. (NYC has 5 counties; each has its own DA's office. ) The internship went well and the kid got a job offer. Kid then interviewed with the other DA's offices in NYC in various bureaus and took a job with a different DA in a different bureau. Kid--well, kid to me, not you--loves the job and is doing well. Having got a job offer from the DA's office where kid did the internship helped convince the other county offices that it would be a good hire. (Not everyone who does one of these internships wants an offer, but more want them than get them. ) </p>
<p>I think that's a pretty common path to the DA's office, as well as to Legal Aid or Public Defenders. (You do a clinical internship with the public defender's office--whatever it's called in your state--while in law school.) </p>
<p>In areas where these jobs are highly sought after, you might even do an unpaid summer after first or second year of law school with the office in order to have a "shot" at the job. Other folks work as interns for criminal court judges and get to know the ADAs that way....and figure out which bureaus they are interested in, not just because of the work, but because of the personalities of the bureau chiefs. </p>
<p>Here at least the path to the US Attorney's office (the federal prosecutors) is quite different. One common path is to get a clerkship with a district and/or court of appeals federal judge and then apply for a job with the US Attorney's office, which almost always requires a minimum of 2 years of work experience for applicants. Some folks do work in "big law" for a few years--maybe paying down the debt a bit--and then apply to the US Attorney's office. The advantage of the first path is that, again, you get to know the AUSAs (Assistant United States Attorneys) when they try cases before the judge you clerk for. That, of course, can be a risk as well, if you "clash" over something with the office. It again, gives you some idea of what work you'd like to do--securities fraud, narcotics, etc. </p>
<p>The paths to these offices do vary--and it's much harder to get jobs in certain US Attorney's offices and certain DA offices than in others. The "boss" DA in New York, in every county, is an elective office. The "boss" US Attorney is appointed by the president. </p>
<p>Hope that at least gives you enough to go on for a start.</p>