Cataloguing
From Tardis Wiki, the free Doctor Who reference
Cataloging is a process that was used by Judoon law enforcement to identify different species, in this case to separate Humans from non-Humans.
This process was used by Judoon who were trying to locate a criminal, Florence Finnegan, a plasmavore who could mimic Human biology, who was hiding among Humans in a hospital on Earth. The Judoon scanned each lifeform's head, marking the Humans who had already been scanned with a black "X" on the back of their hand.
Martha Jones showed traces of non-Human DNA (that of the Doctor) which caused the Judoon to do a "full scan." When she was proved to be Human, she was given some sort of voucher for "compensation." (DW:Smith and Jones)
