Judoon scanner

Judoon scanners were used by the Judoon

Appearance
The device itself somewhat resembled a red, dumbell-sized, sonic screwdriver. When uses, a blue light shone from the end and made sounds much like a metal detector. A black marker was on the opposite end. This was used to mark individuals who had been checked.

Abilities
The scanners could be used to identify an individual's species. It could also identify foreign languages so the Judoon could communicate with any species fluently. The sounds made by the scanner might be how the Judoon interpreted the results, as their ears twitched when a scanner was operating.

Plasmavores could hide their true identity from the scanners by assimilating the blood of a human or other species. Scanners may have had a higher setting, which would force a Plasmavore to assimilate a second time in order to remain hidden. If a foreign species came into close contact with an individual, such as through kissing, it could leave traces that could be picked up by the scanner. At least once this resulted in a long and tedious process to properly confirmthe species of the individual. (TV: Smith and Jones)