 Almost 100 years ago, Professor Edmund Lowkard stated, for the microscopic debris that covers our clothes and bodies are the mute witnesses, sure and faithful to all of our movements and all of our encounters. The Trace Evidence Unit is responsible for collecting and analyzing that microscopic debris to help establish the elements of a crime. Analysis can be performed on the smallest of items, a single hair found on a weapon used in an assault. Glass discovered on the clothing of a burglary suspect, and even microscopic particles of paint found on the victim of a hit and run. To gather trace evidence from a piece of clothing, an analyst will first visually inspect the item. Then they scrape it down to isolate any debris containing potential trace evidence and collect it for further, more extensive examination. Materials that are frequently recovered and examined include hairs, fibers, glass, paint, construction material, tape, cords, rope, wood, and plant material. The Trace Evidence Unit analyzes explosives and explosive residue. They are also responsible for the examination of materials associated with the discharge of a firearm. This is known as gunshot primer residue testing. This kind of test is performed on a scanning electron microscope, which can magnify items up to 300,000 times their normal size. That's enough to detect microscopic particles of explosive primer on a suspect's hands or clothing. A common tool used by analysts in this unit is the comparison microscope. A comparison microscope is essentially two compound microscopes tied together with an optical bridge so that fine details of known samples can be compared side by side with samples of potential evidence. Other microscopes utilized in the microscopy laboratory include a polarizing microscope, fluorescence microscope, and phase contrast microscope. The scientists in the Trace Evidence Unit also utilize modern chemical analysis instruments in their evaluations. An ion chromatograph, for example, is routinely used to identify chemical ions contained in debris from explosives investigations.