The institution of deciding legal questions by a body of ordinary citizens — one of the oldest mechanisms for involving non-specialists in governance, a site of persistent tension between democratic participation and expert judgment, and the institution that forces most directly the question of whether truth is best determined by the community it affects or by those trained to find it.
The jury is democracy's most radical daily practice. It takes twelve randomly selected people, most of whom know nothing about law, and gives them the power to override the state. A judge can be overruled by a housewife, a banker, a retired teacher. This seems either irrational or profoundly rational depending on what you think courts are for. If courts exist to find the truth, the jury looks like an obstacle. If courts exist to legitimize power by making it answerable to the community it governs, the jury is the mechanism.