There is a total of eight various Cyrus Pinkney's plaques to be found throughout the game and their locations have been shown in the above map. After you reach a given plaque, you need to switch into the detective vision and press/hold down the detective vision activating button, thanks to which the object will be scanned. From now on, there will be an entry available in Information about Gotham - Gotham Intel and additionally, you will be able to listen to a recording in the tab with Cyrus Pinkney's profile.
Note - for scanning each one of the plaques, you will be rewarded with, as many as, 15 thousand experience points. Therefore, it is definitely worthwhile to set out to search for these because, in total, you can receive 120000 points!
After you have scanned one of Cyrus's plaques, Batman will be contacted by Alfred, who will inform him about an unsolved case concerning the murder of Pinkney. At this moment, the game also unlocks this character's profile.
There will be another important moment after you have scanned seven out of eight plaques. The game will add a point to the world map (screenshot 1) in the Burnley district. Get to Pinkney's crypt to approach its entrance from the east. (screenshot 2).
Start exploring the Cyrus Pinkney's Crypt, and you will reach, after a few moments, the crypt with the last one, eight plaque. Scan the plaque and listen to the speech recorded by Cyrus, which will conclude this case.