Detective Mode

Detective Mode (formally known as Detective Vision) is one of Batman's most useful gadgets, as it allows him to see people through walls and detect usable and useful objects in the environment. Each playable character can use this mode, and most of them had unique abilities.

Bat Family

 * Batman has the most advanced version of Detective Mode. It shows the skeletons of any and every human. Unarmed enemies are blue, enemies with firearms are orange (red in Arkham Asylum), enemies and weapons such as knives, bottles, pipes, and body armor are highlighted in yellow, and medics in white. The weapon and emotional state of the enemy is also identified. The layout color was blue, but Batman could change it to help tracking chemical substances. In Arkham Knight, Batman uses it to see through multiple layers of the human body. He can switch from scanning the skin, muscles, and skeletal systems. This mode does not appear outside of side-missions, however.
 * Bruce Wayne used Concentration, and it was identical to Robin's and Deathstroke's. The layout was in white. It had no technological apparatus and was probably based on Bruce's heightened senses. Despite this, it could still be jammed through the use of technological devices.
 * Robin uses a version similar to what Batman used, but it highlighted explosives such as the Snap-Flash and propane tanks. In Batman: Arkham City, there were no weapon or emotion indicators, but they were added in Batman: Arkham Knight. His layout was blue.
 * Nightwing could only highlight enemies with his Night Vision and had a motion sensing radar on the top right corner for enemies in close proximity. By the time of Arkham Knight, he also moved to use Detective Mode. His Night Vision had a Yellow/Grey layout.
 * Batgirl used Detective Mode, which works identically to the one Batman uses. Her layout was blue.

Rogues

 * Catwoman uses Thief Vision, a very similar gadget that was built into her goggles. The layout was distorted orange. In addition to highlighting objects and people, blue claw marks appear on ceilings that she could adhere to. However, it doesn't identify thugs with weapons or armor, but it does highlight vantage points.
 * Red Hood used a version that functioned seemingly identically to Detective Mode. It marked deceased enemies as "Neutralized" and highlighted bulletproof enemies in purple. The layout was red.
 * As he re-uses Batman's moveset, Azrael's Detective Mode is identical to Batman's.
 * Joker used a pair of comical looking spectacles that only show the skeleton of an enemy and made a wacky, yet eerie noise every time that it was donned. Joker must remain still while he used his glasses. The layout consisted of yellow and red lines spinning.
 * Deathstroke used Tactical Vision, which was almost identical to Robin's, but with a green layout.
 * Harley Quinn used Psychosis Mode. When activated, the walls filled with carvings (Story DLC only), and prolonged use caused Harleen, Harley's pre-Joker personality try to convince Harley to stop her criminal ways. In her DLC mission, enemies were marked as "Little Piggies", but in challenge maps, the default DM indicators are used instead. Her layout was red.
 * Both Bane's and Joker's gang used experimental x-ray visions, which helped them locate their opponents. However, they could only be used for a limited time, and if fully emptied, they could not be used at all until they had recharged. This layout was blue.

Initiation Incident
Bruce Wayne was capable of using a form of Detective Mode known as "Concentration", which appeared to be a manifestation of his training around the world over the years and Tokagure Ryu training including no actual technological apparatus. That version worked much the same way as his later Detective Vision, and was able to discern armed enemies in orange as separate from ones in blue who were either unarmed or unconscious, as well as different areas of the environment that could be used to interact.

Arkham Origins Incident
Batman used his Detective Vision even in his early times as the Dark Knight. Not only could it read heartbeats, conditions, see through walls, and display skeletons, but it could re-wind a crime scene to see how the death/crime was committed via the Batcomputer. However, the actual people in the crime scene (both the assailant and victim) lacked detail, and appeared instead only as nondescript holograms whose movements were estimated from environmental clues, which meant that it was not completely accurate. This and possibly future versions of the gadget were dependent on the Batcomputer for functional use, as it was unusable when the computer was broken by Bane. Batman's Detective Vision could be blocked by henchmen wearing backpack jammers, and required those henchmen to be knocked out, so Batman could destroy the jammers and use his Detective Vision in Predator Mode.

Deathstroke also had a digital seeing gadget built into his mask called "Tactical Vision", which was most likely stolen/adopted from the Military.

Joker's Henchmen and Bane's Henchmen also managed to make use of a semi-perfect device similar to Detective Vision, though it consumed power, and could only be used for a short time.

Cold, Cold Heart Incident
Batman returned to the regular use of Detective Vision during his hunt for Mr. Freeze.

Arkham Origins Blackgate Incident
Batman brought his cowl lined with Detective Mode back into the field in Batman: Arkham Origins Blackgate to thoroughly scan his crime filled environment.

Detective Mode also had a new use that time. Batman used it to see in dark areas where no light was present.

Arkham Asylum Incident
Batman uses a scaled down version during the Joker's takeover, though it appeared to have multiple filters for different trace evidence types, e.g. breath particles, tobacco traces, etc.

Joker used a special set of glasses, colored red and yellow with swirls, to track enemies.

Arkham City Incident
Again, Batman returned to using the normal Detective Mode to help him identify enemies, but it could also identify armed enemies. As with Origins, Batman's Detective Mode could be blocked by henchmen wearing backpack jammers.

Catwoman possessed a version called Thief Vision that only allowed her to see enemies, but not discern between unarmed and armed, though weapons were a lighter shade compared to people.

Robin possessed a version similar to Batman's, though still inferior.

Nightwing possessed a variant that was grey, with yellow identification, and was an active radar as well.

Arkham Knight Incident
As before, Batman used Detective Mode to help him identify enemies. Crime scene reconstructions were shown in better detail than in Batman: Arkham Origins. It could also do scans of out-of-place markers on deceased victims via a Deep Tissue Scanner, as Batman demonstrated when investigating six grisly serial killing victims, which Batman utilized because directly IDing the victims via DNA analysis was impossible due to their DNA being corrupted, and whatever DNA was left was destroyed via acid on the fingertips. As with previous games, Batman's Detective Mode could still be blocked by henchmen wearing backpack jammers. Additionally, some henchmen may be equipped with a device that could track Batman's Detective Mode (i.e. if Detective Mode was used for too long, all enemies would be alerted to Batman's position) or may wear Optic Deflection armor to render themselves unseeable by Detective Mode (that could be disabled by the Disruptor via an upgrade).

Trivia

 * Clayface had no visible skeleton in Detective Mode, and because of this, his involvement in Batman: Arkham City's plot could be seen beforehand by activating Detective Mode during the fight against Joker and his gang in the Steel Mill.
 * In Batman: Arkham Origins, Mad Hatter had no skeleton, but this is believed to have been a developer oversight, as Karlo had not been transformed yet, and there would be very little reason for any Clayface to impersonate Mad Hatter.
 * When viewed through Detective Mode, Clayface and Solomon Grundy's conditions are listed as "Unknown". These conditions are explained by the lack of organs and being an undead being, respectively.
 * Catwoman and Joker have visual gadgets for Detective Mode (her goggles and his spectacles), but Batman and Batgirl use their cowls, and Robin, Nightwing, Red Hood and Deathstroke have their masks to use the mode. Harley Quinn and Bruce Wayne however, don't seem to use any sorts of gadgets, and their versions simply come from pure natural skill.
 * Detective Mode does not detect the skeletons of rats or other animals. However, during Detective Mode, the bones of dinosaurs were colored blue.
 * The skeleton of Tiny did not appear during Detective Mode, due to sharks' skeletons being more cartilage than bone.
 * In Arkham Origins Blackgate, armed enemies' skeletons are red instead of orange.
 * In Batman: Arkham Asylum, Detective Mode switched color based on the trace evidence that it was searching for. This feature was not seen in any of the other games, however.
 * It seemed that, by the time of Arkham Knight, the members of the Bat Family had upgraded their suits so they could not be seen through X-ray, as they weren't visible through Batman's Detective Mode. This was possibly caused by the "Heat Signature Conceal" upgrade from Arkham City. This would also explain why Jason Todd could not simply locate Batman whenever he appeared in person, despite having his mask equipped with a variation of the vision, as seen in the Red Hood Story Pack DLC.
 * In Arkham Knight, one sound designer who worked on the game stated that the sound that can be heard in the background, when detective mode is active, is the voice of Alfred taken apart and jumbled up. It is unknown what the original audio is.
 * In Arkham Knight, if the player looks closely at the chest of a knocked out thug, they can see the heart of the thug, which is a feature that only Knight has, either because of the previous games graphics, or that Detective Mode is now more advanced. However, the heart feature doesn't show on dead people, due to the fact that they are deceased.

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