Public defenders represent indigent defendants in criminal cases. Public defender offices exist at the federal, state, and local levels; there are also specialized offices that provide legal services in death penalty cases.
Both prosecutors and public defenders have varying views on how they evaluate experience on the other side. In large cities or in competitive offices, employers typically dislike experience with the opposing side. This is especially true for public defenders, perhaps less so for prosecutors.
Many new law students are not sure which side will suit them best and want to explore by interning on both sides. While this is understandable, both sides are also seeking a commitment to their respective missions, which don’t always align. Shadowing an attorney for a couple days on each side might be a good option.