When a person gets stabbed, rips in the victim's clothing may contain clues to help catch the attacker.

Forensic scientists are trying to understand what tears and distortions in the fabric around a stab wound can say about the knife type, angle of attack, and stabbing technique that caused the wound. But the patterns have been difficult to work out, partly because researchers have had to do most of their laboratory experiments by hand, manually stabbing different fabric swatches. But inconsistencies and human error are unavoidable. So a team of forensic scientists and engineers invented a stabbing machine to help standardize this type of research.

While there have been a few other stabbing machines made for science, this new one—built by researchers at the University of Technology Sydney and the University of Santa Cruz do Sul in Brazil—takes the cake. Its pneumatic arm can grip just about any kind of knife, and stab at fabric samples from a variety of angles and forces.

"The machine offers at least 60 possible stabbing positions and the knife holder allows for a range of stabbing implements to be analysed," the authors write.

To put the machine to the test, they used four knife designs and some blue cotton fabric. After jabbing the knives at the fabric from a variety of angles, the authors were able to discern some preliminary patterns.