We'll look at three different areas: jurisdiction, discretion, day-to-day.
A District Attorney's Office (DAO) can prosecute any person that violates their state's penal law within their county.
A United States Attorney's Office (USAO) can prosecute any person that violates certain federal laws, usually contained in the United States Code.
Oftentimes, crimes will overlap. The offices then need to speak and determine the best course a case should take. Which jurisdiction has stiffer penalties? Which jurisdiction has the resources to investigate and prosecute? In my experience though, if the FBI and USAO want a case, they can pull rank and take it.
An interesting difference is the way a case reaches each office. On the state level, the police make arrests and then the prosecutors must choose to prosecute the crime or not. On the federal level, arrests are generally not made until the USAO has given their seal of approval. This allows the USAO to build a strong case and secure indictments before a person is even aware they are a target. A DAO comes into the case well after the police conduct an investigation.
An ADA has much more discretion than an AUSA. In a DAs office, there is an elected District Attorney. Every county in New York State has a District Attorney. Therefore, there are 62 DAs offices in New York State.
Under the DA, there are numerous ADAs. The DA sets policies on various types of crimes and leaves his or her ADAs to operate within those policies. We usually only conference cases with our direct supervisor before proceeding forward. Very few people are involved in the decision making process. The DA has prosecutorial discretion over which cases get prosecuted and how.
The Attorney General of the United States is in charge of all the USAO. Eric Holder, Jr. currently holds the position. The fact that the federal government is involved makes the decision process much more complex. AUSAs do not have much discretion. There are various levels of supervision in each USAO. Then, those decisions are sent to Washington, D.C. for review by the Attorney General's office.
What can get done in a five minute conversation without one piece of paperwork being drafted in the DA's office would take weeks and numerous memos in the USAOs office.
I've posted previously on the day-to-day activities of an ADA (here, here, and here). The day of an ADA and AUSA are very similar. Both spend their time responding to voicemails, emails, and going to court. Also, they spend their time conferencing with witnesses and law enforcement.
The main difference comes in the paperwork and court proceedings. As I understand, AUSAs spend an incredible amount of time drafting legal briefs for court. Every issue is litigated on papers before it is argued in court. In state courts, most legal issues are simply argued orally in open court.
Federal court proceedings are more formal than state court also. There is a large variation between every supreme and county courtroom I practice in. But most of the time, conferences, jokes, and questions about friends and family are exchanged between the judges and attorneys. I've found that the informal conversations between colleagues in state court doesn't exist in federal court.
There are more differences - the application process, credentials needed, the pay (yes the pay!). We'll address more issues in future posts.