Coming soon to a crime scene (and possibly a TV show) near you: a new way for forensic scientists to examine cloth fibers. The new method, which uses laser-like focused beams to peel away tiny fibers layer by layer, could be a powerful tool to track down perps.
Forensic analysts that look at fibers do most of their work with a microscope. They compare fibers from a crime scene against fibers taken from a suspect’s clothes, car or home. An analyst will look at the color and diameter of the fiber, and also try to determine if it is synthetic or natural. They can also use chromatography to pick apart the various chemicals used to dye the fabric. If a fiber’s color has faded in a particular way, this makes it even easier to link two fibers as potentially coming from the same piece of fabric.
But fibers are not as individually unique as fingerprints or DNA.
"White cotton fibers are so common and have so few visual distinguishing features that they are largely ignored by forensic scientists at crime scenes," researcher Brian Strohmeier said in a statement on Tuesday.
What’s needed is a way to better distinguish between two fibers that look extremely similar, but which were produced through very different manufacturing processes. Strohmeier, a scientist at the Massachusetts-based laboratory instrument company Thermo Fisher Scientific, thinks he may have the answer. He’s found a way to drill tiny holes into the fibers to reveal hidden clues to their origins. Strohmeier presented his research on Tuesday at the AVS International Symposium and Exhibition, a materials research conference.
The new method is a twist on an old technique called X-ray photoelectron spectroscopy (XPS), which blasts samples with X-ray beams to figure out the chemical signature of a fiber. But this technique only examines the surface of a fiber. To go deeper, Strohmeier and his colleagues drilled into the tiny fibers with a focused beam made up of clusters of atoms of the gas argon. By turning on the beam for longer and longer periods of time, researchers can expose deeper and deeper layers within the fiber. Then those layers can be analyzed with conventional XPS, allowing an analyst to get a truly in-depth look at a sample.
Using their method, Strohmeier and colleagues were able to differentiate between materials that came from different manufacturing processes and were treated with different chemicals, but which otherwise looked identical. More work needs to be done beyond this proof-of-principle test before the cops can add this to their forensic tool kit, but Strohmeier says the method has amazing potential.
It seems there’s no end to the stories that forensic analysis of fabrics can tell – and not all methods rely on peering at tiny fibers. In 2009, scientists from the University of Otago in New Zealand found that by analyzing the rips in the clothing of stab victims, they could get a rough idea of what sort of implement was used, allowing them to distinguish between cuts made by hunting knife, kitchen knife or screwdriver.
Criminals, beware – your clothing is more than willing to snitch on you.