Justice Anthony M. Kennedy, writing for the majority, calls the DNA test "a legitimate police booking procedure." And the Court also noted that the DNA test is fairly non-invasive, that it involves no surgery. And that's true! But it's important to analyze why things like fingerprinting or photographing are police booking procedure: it's exclusively for identification. DNA tests are worthless for identification; they are only used to match one sample against another. That makes them valuable for solving older cases, but entirely unnecessary as a standard booking procedure. As a matter of protocol, DNA results are entered into a database, and automatically checked against it for matches, which is what happened in the King case.