from the what-about-concealed-dog-licenses? dept.
lee1 writes "It turns out that the UK has a DNA database — for dogs. And this database was recently used to apprehend a South London gang member who used his dog to catch a 16-year-old rival and hold him while he stabbed him to death. The dog was also accidentally stabbed, and left blood at the scene. The creation of human DNA databases has led to widespread debates on privacy; but what about the collation of DNA from dogs or other animals?"
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"