How are Psykers detected/found?

Question

We were playing a Black Crusade roleplaying game (I am the GM), and the discussion came to how the Imperium finds the Psykers hidden within the populace. The Lexicanum wiki states on their info about black ships that they are offered as tithe from the planetary governors to the black ships, but there is no mention of how to actually find them. The Lexicanum article about Psykers is not enlightening, either.

What are the planetary governor's methods of finding Psykers? This might become very relevant as one of the player characters is a heretic Psyker and is at risk of being discovered, although with a very small chance.

Do note that this is more of a lore question.

Answer 1

In Warhammer 40k the Imperium governments are responsible for giving their psyker to the Black Ship or the Inquisition, so it's mainly up to you. ;)

Each world will have it's own method. Don't forget that an untrained Psyker is far more dangerous than a trained one (even a Chaosian one); just look at the psychic phenomena table, or the next one: perils of the warp, it goes to just have some temperature drop to mass demon possession, with some funny thing like blood rain from all ceiling ;)

As long as your Psyker doesn't use his power, it'll will be very very unlikely that he will be found. Psykers are rare, and the ones with warp sense (Psyniscience test for free action) even rarer (except for the player, they always take warp sense ;) )

You can also have checkpoint at the spaceport, or before entering some sensible zones; these checkpoints may have a Psyker checking the visitors. But don't forget that they generally have better uses, if you have Psykers at checkpoint it must be very important.

But if your party does something out of the ordinary, something noticeable by a human, like all the food going sour around the Psyker, an inversion of gravity, someone hit by something invisible, or the roulette in the casino giving always the same winner, the chance that the populace are fleeing the zone screaming 'Psyker' is high.

And if there is reasonable suspicion of a Psyker being somewhere, the Inquisition will be there, and that is a risk.

Also, your group is not the only one trying to undermine the Imperium, so an Inquisitor may be there coincidentally. (The inquisition group may also be there for à false alert, and digging some heretic stuff.)

Answer 2

In Dark Heresy and Rogue Trader there is the skill Psyniscience which allows the user to track Daemons and Psykers. However, its range is short, in the order of meters or tens of meters. Maybe your Psyker could avoid being discovered by avoiding areas populated by other Psykers (who possess this ability).

Or the Psyker in question could turn himself to the Inquisition and repent for his sins, that's also an option. May the Cleansing Flames purify his tainted soul.

Answer 3

Your main question:

What are [a] planetary governor's methods of finding Psykers?

A Planetary Governor should normally have access to the following resources to conduct this absolutely necessary component of Imperial Governorship: Planetary Defense Force (direct command), Adeptus Arbites (independent), Adeptus Astra Telepathica (liaised to Planet Govs for communication). This should be true of all worlds that have an actual Planetary Governor, regardless of size, since all Imperial Worlds need to be able to defend themselves, guard against internal corruption, and communicate with the greater Imperium (respectively). Even with only these "bare-essentials" Adepta, a prudent Planetary Governor should be able to have at least one Psyker available to Psyniscience check for others. As noted in Alkano's answer, one of the better ways to screen for this is through spaceport customs.

There could also be other Imperial factions involved with a given planet's Psyker-gathering activities:

• The Adepta Sororitas and Adeptus Ministorum may well just purge with fire anything they even suspect might have the stain of the witch.

• The Imperial Guard actively uses Sanctioned Psykers, but given their rep among general troops, IG reactions could run the gamut from Sisters of Battle-level zeal to legitimate sympathy.

• Adeptus Astartes gather Psykers to be Librarians, but they generally don't take from planets that have Planetary Governors, since they have their own worlds to recruit from.

• Adeptus Mechanicus is outwardly nominally afraid of Psykers, since most cogboys who get involved with Warp-anything go the route of the heretek-al Dark Mechanicus and/or are censured.

• Inquisition has the entire Ordo Hereticus dedicated to hunting down Psykers, along with the assistance of their Chamber Militant, the aforementioned Sisters of Battle.

I know that in Dark Heresy 1e and 2e you can use the Skill 'Psyniscience' to detect changes in the Warp. Here's the entry for it from Black Crusade Core Rulebook, page 107:

PSYNISCIENCE (PERCEPTION)

Those with the Psyniscience Skill sense the currents and eddies of the Warp and Immaterium. Characters can use the Skill to detect the presence or absence of daemons, the use of psychic powers, psychic phenomena, disturbances, or areas where the flow of the Immaterium has been unsettled or disrupted. Unless otherwise noted a character can use the Psyniscience Skill to detect entities, locales, and events up to a number of kilometers away equal to their Perception Bonus. A GM may increase this range for particularly powerful events or creatures. The general results of Psyniscience tests are summarised on Table 3-4: Psyniscience (same page: 106).

Skill Use: Full Action

• 1 DoS: Awareness of Immaterium disruption or number of entities present

• 2 DoS: Approximate direction of the phenomena or creatures

• 3 DoS: Rough location of the Warp creatures or beings affecting the Immaterium

• 4+ DoS: Exact position of the creatures or psykers present

I don't know what the standard distribution birth rate of Psykers is in the Imperium, so it would be difficult to answer how many are likely to be found wherever it is that your game is taking place. However, as you stated, the Imperial Tithe requires that each planet under the control of the Imperium does three main things, one of them being the gathering of Psykers.

Every Imperial planet must agree to turn over or mercilessly slaughter with malice aforethought all unsanctioned psykers. The reasoning behind this is that without (and sometimes even with) the divine sanctioning of the holy Emperor, even the most well-meaning psyker can accidentally become a conduit for a Realspace/Warp invasion. Entire planets can be and have been lost because of one errant soul that slipped through the dragnet. Needless to say, this is a massive problem, and it's better to have a few false positives rounded up and killed by your paranoid, uneducated populace over losing entire cities/continents/planets to a phenomena.

At the same time, the more people on the planet, the more likely you'll find a Psyker. If you assume that the same birth rate for Psykers occurs everywhere, then the best place to hunt for and find Psykers would probably be Hive Worlds, as a team of Psykers with good Psyniscience and Perception could probably canvas the entire cloud-scraping city relatively quickly. Given that this is also a requirement, and I'd assume that most hive cities already have some sort of protocol in place for culling and finding Psykers.

Lastly, it seems to me in the fluff that people suspected of being Psykers are often killed by the people around them before they have a chance to manifest something terrible. Sometimes the issue is that they are found and safely captured, but holding them until the Black Ships arrive takes too long, and something bad happens instead. Knowing the level of sensitivity that the average Psyker now has with regards to the Psyniscience Skill, I feel like tracking an active and/or powerful Psyker through even a hive city wouldn't actually be that hard.

Answer 4

Have you read the Eisenhorn trilogy? I don't offhand recall details of how the planetary governors did their jobs, but I certainly remember Eisenhorn scanning for psykers. This is generally a good book for getting a grounding on how the Imperium works, away from the front lines and the continent-shattering weaponry.