Final answer:
The most important thing for a foreign service officer to do when a US tourist is arrested is to request from host country authorities a summary of the evidence against the accused.
Step-by-step explanation:
The most important thing for a foreign service officer to do when a US tourist is arrested is to request from host country authorities a summary of the evidence against the accused. This is important because it allows the officer to gather information and assess the situation. While it is also important to notify the family of the accused and retain a local attorney for the accused, obtaining evidence summary is crucial in order to provide appropriate assistance.