Mechanismo is a catch-all term for robot Judges in Mega-City One, as well as for a storyline about them in the 1990s that led into Wilderlands. They were both proposed by and led to the demise of Chief Judge Hilda Margaret McGruder and, despite the flaws of the programme, remain one of the city's weapons of last resort.
Their name comes from the term for Dredd's brain patterns and demeanor that was programmed into the early units: literally, a portmanteau of "mecha" and "machismo". It later became the accepted name of the machines themselves.
The Mechanismo robots were humanoid in shape and were armour-plated, with insignia resembling those on human judge uniforms. They had infra-red vision, built-in weaponry including missiles and gas grenades, and carried large machine-guns. They were issued with Lawmaster motorcycles.
Their original appearance was designed by artist Colin MacNeil. A later upgraded version, the "Mark 2A," was designed by artist Peter Doherty and the later "Mark 8 RV" was designed by John McCrea. Although the script described the Mark 2As as looking "friendlier" than their predecessors, artist Peter Doherty's design looked sinister and inscrutable.
Following the cataclysmic disasters known as Necropolis and Judgement Day in which many Judges lost their lives, Justice Department was severely under strength. To supplement the numbers of human Judges and bring the escalating crime rate under control, McGruder authorised Tek Division to build robot Judges, which once ready would be vested with full judicial powers: authority to arrest, convict, sentence and if necessary execute criminals. The whole project was developed in strict secrecy under the auspices of Tek-Judge Greel, Stich and Quiggley, and was not revealed to the public or to rank-and-file judges until the first batch of robots were ready for duty in late 2114.
The Mark I robots were field-tested under strict supervision. Although they made a promising start, Judge Dredd was not impressed with the idea and was aggressively resistant to the whole concept - ironically, the robots were based on his own brain patterns. Stich and the Chief Judge ignored his concerns.
Dredd was soon vindicated when the robots began to break down, unable to properly process the 'mechanismo' from thinking like Dredd, and two of them began slaughtering innocent civilians indiscriminately. When the robots were ordered to shut down, the two rogue units ignored the order and had to be destroyed. Dredd personally gunned down unit number 8. However, McGruder simply paid compensation to the victims' families and ordered Stich to rectify the fault in the robots' design and programming.
Her ambitions suffered a further setback however when the damaged Number Five reactivated itself and embarked on a second killing spree later that night, escaping from Justice Department premises and shooting Judges and civilians alike, believing it was 'judging criminals'. This time the robot escaped into the sewer system and was not recaptured.
After the massacres perpetrated by the Mark I robots, Judge Stich was unable to bear his share of the responsibility for the disaster and he went insane. He was committed to a psychiatric ward, from where he would persistently escape and search the sewers for the rogue Number Five.
It was generally assumed that McGruder had learned her lesson and that the project had been discontinued. It suited McGruder to allow people to think so. However, she still authorised the development of Mark IIs, this time under the purview of Tek-Judge Quiggley. After another year of work, Quiggley almost had the improved robots ready for a second field test when Number Five re-emerged from the sewer and began a third campaign of murder. This time Number Five had learned to go to ground after each attack, and all efforts to locate it failed.
Taking personal charge of the search, McGruder brought forward the new robots' field test and deployed them on the streets, reasoning (wrongly as it transpired) that the best way to anticipate the next move of a robot was to use other robots to hunt it.
Dredd was appalled to learn that the Mechanismo Programme had continued in secret, and openly demanded the Chief Judge's resignation. She refused.  Resolving to stop the Mechanismo Programme, Dredd decided to discredit the Mark II robots by finding Number Five before they did. He realised that the robot was still using the sewers to move around undetected, and began his search there.
However, one of the Mark IIs found Number Five at the same time as Dredd. Ignoring Dredd's shouted order not to fire, the Mark II destroyed Number Five. Dredd then illegally destroyed the Mark II and persuaded the suggestible Judge Stich -- who had witnessed the entire incident -- that he had seen Number Five destroy the Mark II and then Dredd destroy Number Five.
Following the apparent failure of the Mark II, Judge Quiggley was demoted and Greel was put in charge, again in secret. In 2116 his Mark 2A robots were ready. They had a radically different appearance to the first two batches and were given names instead of numbers to make them less intimidating to the public.
To much controversy and consternation, the new Mechanismo were again deployed on the streets and were also used to guard the Chief Judge in place of human Judges. This finally brought to a head the widespread concerns about Chief Judge McGruder's deteriorating judgement - however, by this point Stich had been interrogated at length by Greel and subjected to truth drugs until he remember what really happened to Number 5. Implicated in criminal damage and perjury, Dredd was arrested by the new Mechanismo. 
McGruder went on a diplomatic visit to the colony Hestia on a diplomatic visit, hoping to sell some Mechanismo units to the planetary government. However, when her party was threatened by a stampede of large animals, her robot bodyguard took no action to protect her, and in a dune shark attack a Mechanismo seemed to deliberately miss its shot. This escalated to a Mark IIA deliberately sabotaging the spaceship Justice 4 so it would crash in the Hestian wilderlands and then attempting to assassinate McGruder. Ironically, it was Dredd who saved her
On her return to Mega-City One, Greel was arrested on suspicion of sabotaging the robots and attempting to kill the Chief Judge. He was released when 72 hours of intensive interrogation found no evidence to prove it (he was demoted to Traffic Division in the Pit anyway), and the working theory became that the robots had decided she was a threat to the city and needed killing. and he was released (but demoted). The Mechanismo project was officially aborted.
Although no longer vested with judicial powers, the robots were shown in later stories to still be used in outer space, Cursed Earth facilities, guarding one of Judge Death's prisons (as he couldn't possess them), and as combat units in dire emergencies. When the xenomorphs invaded the Grand Hall of Justice, Judge Giant activated four Mechanismos from storage to drive the aliens back. 
During Chaos Day, robo-Judges were rushed into service after the destruction of the Statue of Judgement and were in continuous use in the carnage that followed - including operations with Judge Dredd, against human perps.
Mark 8 RVEdit
Years after Chaos Day, Barbara Hershey - one of those who'd tried to depose McGruder over Mechanismo - commissioned the Mark 8 Responsive Version's. In addition to heavier armour and improved weaponry, these robots were designed to have basic empathy with the citizenry so they would not turn murderous again. Mechanismo Judge Harvey was given to Dredd as a rookie, to test if they were useable on the streets. (Dredd gave an overall failing grade out of personal prejudice but this was ignored by Hershey.)
In the end, the Mark 8 RV's turned out to be too human to operate in Mega-City One: they began to aggressively rebel against the inhuman conditions and bureaucracy that the citizens lived under. The Mechanismo Jerry intervened on the side of a desperate hostage taker and refused to accept a stand down order from Dredd, forcing Harvey to destroy him.
They continued to be rolled out with tweaks and remained popular with citizens. Stats showed they were indeed bringing crime down. Dredd remained sure that the robots might take over, citing how this had happened in Gautamala, and was irritated to find new robo-Judges being patronising to him. Matters came to a head when the new Chief Judge, the pro-Mechanismo Logan, appointed Harvey to the Council of Five; outrage and talk of impeachment spread through the city, while Harvey begged first Dredd to publicly support Logan (which he would not do) and Logan to drop him (which he would not do as it would lose face). Judge Farrow would lead a dozen Judges in an abortive coup over the issue, similar to the attempted conspiracy against McGruder twenty-five years before.
At a ten million strong anti-robot march, Harvey - running security detail and facing hostility with some Judges - saw his chance to, in his mind, save Logan's government when a fake suicide bomber arrived. The robot blew himself up 'shielding the crowd' from the bomber (who, having caused a fatal stampede, could be legally sentenced to death) so that he would no longer be a political liability. Logan and Dredd were both left impressed by Harvey's dedication to duty. The new Chief Judge decided to keep a Mechanismo as an advisor but not on the Council, "rubbing it in their [the city's] faces." 
- ↑ Judge Dredd Megazine (vol. 2) #12
- ↑ 2000 AD #891-894; Megazine #57
- ↑ Judge Dredd Megazine (vol. 2) #10
- ↑ Megazine #12
- ↑ Megazine #12-17
- ↑ Megazine #22-26
- ↑ Megazine #37
- ↑ Megazine #37
- ↑ Megazine #41
- ↑ Megazine #43
- ↑ Megazine #57
- ↑ 2000 AD #904
- ↑ 2000 AD #904-915; Megazine #63-67
- ↑ 2000 AD #914
- ↑ 2000 AD #915
- ↑ Dead Ringer
- ↑ Tour of Duty
- ↑ Death Trap audio drama
- ↑ 2000 AD #1322-1335
- ↑ Harvey, progs 2024-29
- ↑ Machine Law, progs 2115--