Laser printer fingerprints
Researchers at Perdue University can identify what model of laser printer produced a particular printout. The researchers have discovered that the intensity of the print produced by a particular printer varies in a unique manner (banding) as the page is printed. This is because printers are made from parts manufactured to a relatively low accuracy, in order to keep costs down.
The discovery resulted from research done for printer manfacturers to find ways to reduce the banding, which is often not visible to the nacked eye. At the moment, the characteristics of the banding change when a toner cartridge is replaced, but it would be possible to add deliberate imperfections to their printers, to allow the authorities to identify exactly which printer that was used to produce forgeries or documents presented as evidence in criminal cases. The American Secret Service is now working with the researchers, giving them guidance as to the “right direction” for the research, which they hope will provide better methods for tracing documents and counterfeit bank notes.