A common situation that comes up in criminal cases is a search conducted by police, where evidence is found.  More often than not, police find incriminating evidence through a voluntary search of a person, their vehicle, or their home.
When I ask clients why they would consent to a search, when they know they have something illegal, the top two answers I get are: “I didn’t know I could say ‘no’” and “I thought if I said ‘yes’ then they wouldn’t search me.”
Understand that when law enforcement officers ask you if you agree to let them search you or any of your belongings, you always have the right to say “no.”  Your “no” does not require an explanation or a qualification.
When you say no, a law enforcement officer may still choose to conduct a search.  Do not interfere with the law enforcement officer’s search, but make it clear you don’t agree. If that search is not legal, then it can be challenged in court to have the evidence thrown out.