Human-Alien Interrogations during and post the Second Contact War
Imagine needing to quickly extract information from an Alien species with no known common bases other than body shape, and how you would go about it.
And then apply that to a species that lacks a mouth, and due to security risks have to be killed or kept unconscious under sedation.
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Until Humanity discovered that the Sectoids were just part of an invading conglomerate, this was what the Alliance faced, with the live capture of a Muton, there was hope of communication in the distant future… And then the Alliance captured a 'Thin-Man' successfully, and after that, managed to break the hold of the Ethereals over one.
X-Com [And it's new iteration, Cerberus], is authorised to do anything it wants to 'Aggressive Non-Human species', which allowed for torture to try and secure any actionable information, or in truth any information at all from the aliens they captured, and with the capture of aliens that spoke human languages, some would say this was gleefully put to use until some thin-men could be coopted, where they were also used in the interrogation of alien species.
Eventually, Human psionics were discovered, and mind links [Now known as Mind-Melds] became the new interrogation standard, until finally after the war Mind Taps were refined based on the Gollop Sphere.
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Currently, the Commisarant and X-com/Cerberus both use mind taps as their main interrogation tool, as they offer a guaranteed means of accessing the subjects mind without restraint if used appropriately, however understanding the results may take time. For faster interrogations, invasive Mind Melds are used, however information extracted through these melds is considered suspect, as the meld can be resisted in a variety of fashions. Due to laws, these interrogation methods are neither admissible, nor seen as breaches of privacy outside of Human, Asari or [Some] Terminus systems, and are supported due to lack of physical and psychological harm.