A Customs exam is either an X-ray, Tail Gate, or Intensive exam.
CBP (Customs Border Protection) selects shipments for examination based on a targeting system that applies a score to each shipment. If the score is over a certain number, it triggers further review and possibly an exam.
CBP keeps the specifics of the targeting system confidential, but certain factors tend to affect exam selection. For example, first-time importers are inspected at a much higher frequency than importers who have an established record shipping into the country.
CBP collects data from sources including:
Based on the data and subsequent targeting score CBP may then put a variety of holds on the shipment for further action before it can be released or possibly detained for an X-ray, Tail Gate, or Intensive exam.