My concern is not the DNA from the crime scene, but the mechanism used to identify a suspect for further investigation and obtain a sample to compare. There was no DNA match in any state or federal database, or apparently anywhere else.
There were samples in a DNA database, although not maintained by the government. Certainly, similarity alone could not be used to convict someone. It gives hints on directions for the investigation to take. Warrants have historically acted to protect citizen privacy and to limit police powers to invade homes, offices and bodily integrity of suspects. If said suspect, however, leaves traces of evidence (even as unintentional as fingerprints or DNA samples from discarded items) in non-private areas there are gray areas of the Fourth Amendment. I think the court has been erring on the side of prosecution where the evidence is no longer in the control of the suspect and left in a public place. Is a private database of DNA, whose sample is comtributed not by the suspect but by a possible near connection to the suspect cross over the gray line into privacy? This is what the court will have to decide, one way or another, but it is probably not going to allow an argument that a suspect has an interest in privacy encompassing all his or her relatives’ voluntary disclosures.
I agree with your take on this. Big potential for abuse and I believe there are very real concerns about privacy and due process.