Judoon

The Judoon were a race of rhinocerous-headed humanoids employed, as the Doctor put it, as "police-for-hire" (or, he added, "interplanetary thugs").

Biology
Judoon were two-metre high humanoids with a stocky build and rhinocerous-like heads. They had large lungs to help with breathing even in environments with low levels of oxygen.

Behaviour
Judoon were brutish and meted out punishments that might seem cruel to some races (for example, physical assult incurred one of the Judoon's favourite punishments, execution). However, they still operated under Galactic Law. They reserved 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 target.

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. (DW: Smith and Jones)

Technology


The 'execution' punishment the Judoon were 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 had 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 spacecraft were 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 H2O Scoop to transport buildings across space and shield them with force fields as required by Galactic Law. (DW: Smith and Jones)

Behind the Scenes
Doctor Who fans have noted a visual similarity between the appearance of the Sontarans and the Judoon. No reference to this appeared on-screen.

The Judoon are rumoured to appear later in The Sound of Drums or Last of the Time Lords.