Borescopes usually have a light source and a series of rods that allow magnified, illuminated viewing inside very small holes and apertures. Some borescopes use spaced achromats and others use the Hopkins design so the objective lens forms the image from one end of the borescope to the other. These features make the borescope a useful tool for crime investigation, but the use of so many tiny, expensive lenses and a lack of precision have limited its use.Gradient Lens Corp. of Rochester, N.Y., has developed a proprietary manufacturing process and patented technology for producing precision lenses and borescopes at an affordable cost. The company's Hawkeye precision borescope replaces all those lenses with a few simple glass rods. Most lens aberrations, which cause a loss of image quality, are eliminated by the company's manufacturing technique and approach to balancing chromatic aberration.Bob Stanton, an examiner with the Monroe County Crime Lab, also in Rochester, uses the Hawkeye borescope to examine the grooves or marks inside a gun's barrel, which make unique marks on any bullet fired from a gun. In a typical investigation, examiners fire a test bullet from the gun in question and then look for a match between the marks in the barrel and those of a bullet used in a crime.The instrument can also be used to examine nonfunctioning weapons. "Sometimes we have a weapon that is damaged or that can't be taken apart," Stanton said. "The borescope enables us to look into even small, confined areas with precision." With a 90° adapter, Stanton can look into a gun's bore, firing hole or other areas that require this angle for viewing.The safety element It can be dangerous to fire a damaged gun. One examiner who works for a law enforcement agency in Canada said the Hawkeye not only lets him look for a manufacturer's stamping, residue and other evidence, but also offers a measure of safety. Sometimes investigators run across a situation where a firearm is damaged or has been tampered with, making it more difficult to verify its match with a bullet and dangerous to do a test firing. In one case, an examiner lost several fingers when firing a damaged weapon."With the Hawkeye borescope we can look at a weapon before we fire it and find out if there is a weakness that would make firing a weapon dangerous. The borescope allows us to get some good, solid information, even when it isn't safe to fire the weapon," the investigator said.The time elementInvestigators sometimes have to search cars for drugs, and disassembling a car for this purpose can take as long as three days, according to one investigator. But now they can insert the borescope into the anticorrosion holes in a car and explore the interior in a fraction of the time. "The borescope saved a great deal of time, as well as helping ensure that we were doing an exhaustive investigation," the examiner said.