Tip #1: Calmly Refuse to Be Searched
If you are randomly selected for a search, you have the right to refuse. When asked to submit, you may clearly and calmly say “Officer, I do not consent to any searches. I’m going to exit the station.” Do NOT talk back, raise your voice or physically resist.
Tip #2: Realize that Refusal Is Not Guilt
WMATA states that “[a]nyone who is randomly selected and refuses to submit their carry-on items for inspection will
be prohibited from bringing those items into the station. Customers who encounter a baggage checkpoint at a station entrance may choose not to enter the station if they would prefer not to submit their carry-ons for inspection.” Such a refusal will not constitute probable cause for an arrest or reasonable suspicion for a forcible detention. (emphases added)
Tip #3: Shut Your Mouth and Your Wallet
Whether or not you consent to a search, you do not have to answer any police questions or give any information (e.g. your name, ID, citizenship or immigration status). But remember, anything you say can be used against you.
Read the rest here. The linked document and text are from a 2008 document produced by FlexYourRights.org. The linked WMATA statement, however, is the current, December 2010 “Bag inspection talking points” document; while there are subtle differences between the current proposed inspection process and the one proposed two years ago, the FlexYourRights.org document still appears to be good advice.