The Judoon appeared in Smith and Jones(2007)The Judoon are a race of rhinocerous-headed humanoids employed, as the Doctor put it, as "police-for-hire" (or, he added, "interplanetary thugs"). Judoon are two-metre high humanoids with a stocky build and rhinocerous-like heads. They have large lungs to help with breathing even in environments with low levels of oxygen.
Judoon are brutish and meted out punishments that might seem cruel to some races (for example, physical assault incurred one of the Judoon's favourite punishments, execution). However, they still operated under Galactic law. They have the right to execute without proper trial. The Doctor suggested they operated in terms of guilt by association, claiming they might kill everyone in the Royal Hope Hospital for assisting their suspect.Their language was composed of many one-syllable words ending in a long "o" sound. Each sentence was composed of several of these words hyphenated together.The Doctor described them them as logical but stupid and they seemed to favour methodical patterns of behavior, to a fault.
The 'execution' punishment the Judoon are so fond of was delivered using a directed energy weapon with a red beam. The Judoon had scanners which would tell the Judoon the species of the scanned being. However, the scanners could be fooled by previous close contact with another species. Metamorphic beings capable of altering their internal biology using assimilated biomatter could also deceive the scan. They also had translation devices which worked by analysing the recorded voice of a being. The translation was reciprocal.
In general, their technology was a dark red or black colour, and most instruments, such as their weapons, scanners and translators, were thick and pen-shaped, simiar to a large sonic screwdriver. They did have a pen, a thick marker pen, used to mark "catalogued" people - those who had been scanned and deemed to not be a suspect - on their right hand.
The Judoon also have a contact device that reaches every Judoon helmet, allowing the Judoon Captain to give orders with a press of a button, albeit not pen-shaped. It is the same device as the language assimilator.
Their spacecrafts are large cylindrical craft, with four boosters at the bottom and four claws at the bottom which seved as landing gear. Each craft could hold several thousand Judoon in troops of several hundred each. Three of these craft landed on the Moon.The Judoon could also use H20 scoop to transport buildings across space and shield them with force fields as required by Galactic law.
Smith and Jones(2008):On meeting the mysterious John Smith(the Doctor), medical student Martha Jones finds her life turned upside-down. A lightning storm and some upside-down rain send the Royal Hope Hospital to the Moon, and Martha must cope with the brutal Judoon, an intergalactic police force, and a blood-sucking Plasmavore. John Smith(the Doctor), her ally in the crisis, soon proves he is no ordinary patient...