If, after giving consent to search, a person becomes nervous and revokes or limits the scope of the search, can this reaction be used by the offi cers as an indication of probable cause to obtain a...

If, after giving consent to search, a person becomes nervous and revokes or limits the scope of the search, can this reaction be used by the offi cers as an indication of probable cause to obtain a search warrant? Can a person validly revoke or limit the scope of their initial consent to search?