The Mind Probe was a piece of scanning technology that detects traces of criminal activity from the mind of a person being scanned.
The mind probe was designed to find crimes that have been concealed from the law and thus bring the perpetrators to justice accordingly. It was standard activity to have those entering penal colonies to undergo it (unless they have a clearance code given before they land).
Three million years into the future, the crew of Red Dwarf were looking to solve the mystery of who the occupant of an escape pod was - a deranged cyborg killer, or a female prison guard. The Dwarfers decided that the safest cause of action was to use Starbug to travel to the nearby space prison, Justice World, which was the original destination of the occupant of the pod.
When they arrived a Justice World, the AI computer of Justice World forced the crew to wear Escort Boots before they could leave the hangar. It then scanned the crew with the mind probe to uncover any potential previous criminal activity, but found none in Kryten or the Cat, and allowed them to go free.
When it scanned a deeply concerned Dave Lister, it found evidence of petty criminal acts from his adolescence in Liverpool, but let him pass anyway. This may have been because he already served his time for when he was caught stealing cars, as Kryten points out. The mind probe also uncovered he fact that the Lister had once stolen the contents of an entire hotel room since the flat he was living in at the time was unfurnished; however Justice World clearly does not consider this a serious enough crime to punish Lister for, and lets him go free despite his misdemeanors.
When the mind probe scanned Arnold Rimmer, it detected his guilt for the role he played in the Cadmium II radiation leak that killed the crew of Red Dwarf and charged him with second degree murder, with 1167 counts - one for each member of the crew except Lister and Rimmer himself. With 8 years per death, the total sentence was judged to be 9,336 years. Noting Rimmer's hologrammatical status, these many charges were to be served consecutively, and Rimmer was placed in convict clothes and taken to his cell in the Justice Zone, where no criminal act could be performed.
Rimmer was saved from spending a few ice ages in prison thanks to a defence by Kryten, who asked Justice World for a trial where he pointed out one of the faults of the device. It detected Rimmer's guilt but as Kryten pointed out, Rimmer was only a Second Technician in charge of Z Shift, and he was too inept, unqualified and subordinate to really be to blame for the accident (and that it was the fault of the one who ordered him). Kryten successfully argues the case that the Mind Probe detects guilt, but that does not necessarily mean culpability. Justice World accepts Kryten's case, agrees that Rimmer could not be to blame, and frees Rimmer. ("Justice", Series IV)
- The Mind Probe would seemingly be useless for sociopaths as they do not feel guilt over their crimes.
- The technology is apparently similar to a number of others seen aboard Red Dwarf, such as the Dream Recorder in the episode "Parallel Universe", which could read a mind and record dreams from it. The Mind Patch in the episode "Holoship" also recorded and stored minds, and could meld them together. Other examples include the Hologram Simulation Suite, which could scan the mind and swap memories. ("Thanks for the Memory") The same procedure could also be performed in the Science Room. ("Bodyswap")