Serial Number Science: WSP says bad guys who file them off are just wasting their time

SEATTLE -- Forensic scientist Kathy Geil has a passion for serial number restoration. "What I'm going to do is add a little water to the surface," she said. Geil, who works at the Washington State Patrol Crime Lab, has already restored more than 400 numbers -- half of which have been on firearms. "What I'm trying to do is create a nice, smooth surface in which to see the numbers. So we try to create a mirror like finish. It seems counterintuitive, but I'm actually removing more medal so that I can visualize the numbers," she said. It's a highly specialized skill that isn't as easy as it looks. "It's very techy -- you have to really practice and play with it and learn how to do it because the combinations of chemicals in your lab might be different in another lab, because your surface is changing. In a 110 degree weather, this is going to react differently than in Seattle," Geil said. Because of the science behind it, Geil said it's rare that a serial number can't be restored. "The science of it is, as you're stamping a number into the material, you're changing that material to hold that number. Below that, you're actually affecting the material. So, in medals you're crushing the crystalline structure and that's what we're restoring," she said. The technique can be applied to everything from metal to plastic, so the Crime Lab is able to restore numbers on other items as well. "It's not unique to serial numbers on firearms. Part numbers, proof marks, other markings on material can be restored." It's just one more way the bad guys can't win. Not only are there stiffer penalties for those caught messing with a serial number, but in the hands of science, the numbers come right back -- and that makes this forensic scientist very happy. "It's pretty fun to have it reveal itself and then know that you're helping close a loop in a case. It's kind of cool."