Cellphones regularly have posed perplexing issues to courts struggling to apply our constitutional rights to this ubiquitous and overwhelmingly important modern technology. The already thorny area of how the Fifth Amendment reaches conduct short of an individual actually speaking to the police or taking the witness stand has proven no exception. The right against self-incrimination generally covers potentially incriminatory testimonial communications—assertions of fact deriving from the person's mind—and not demands to produce something that already exists. Unless, as is typically the case, the very act of producing that thing implicitly communicates incriminatory information.