A Ruling on DNA Samples Re "Why the Court Was Right to Allow Cheek Swabs," by Akhil Reed Amar and Neal K. Katyal (Op-Ed, nytimes.com, June 4): The claim that forcing arrestees to provide DNA samples can help exonerate the innocent ignores the reality that innocent people can and routinely do voluntarily provide DNA samples that exonerate them because they do not match the crime scene evidence. There is absolutely no need for a law to force them to do so. And the assertion that these laws deter crime ignores the only research on the topic, a RAND Corporation report that said the effect was "minimal." The Fourth Amendment demands that we examine the justification for a law that allows the government to seize, analyze and databank the DNA of thousands upon thousands of innocent Americans without a warrant or any reason to think that these invasive searches will uncover any evidence of a crime. That examination should rest on facts and research, not baseless assumptions. MICHAEL T. RISHER Staff Attorney, American Civil Liberties Union of Northern California San Francisco, June 6, 2013