Batman Arkham City

This is the first part of the "Shot in the Dark" side quest.

The quest is started when you hear a loud gunshot. Oracle will highlight a region for you on the map in which you then need to search for a body. Once you analyse the crime scene, you will need to trace the bullet back to its origin using detective vision in order to find another clue.

You need to repeat this 3 times to get this achievement. The first clue is a shell casing, the second is a tripod mounted on a wall, and the third is an imprint in the snow (you must scan the ricochet first - point 6 on the map below). They are all close but to a little before the end of each trajectory so look around the area.

You have to wait to hear the shot before investigating each crime scene. I'm not sure what triggers each shot. For me, the first shot came early in the campaign, but the second didn't come until after I finished the campaign and the other side quests (except the Riddler one). I wasn't doing anything special at the time, just collecting riddles (I had just under 200). I wasn't anywhere near the crime scene. The third shot came very soon after that, when I had just over 200 riddles. If anyone has an idea what the trigger is please let me know!

Edit: thanks for the comments - it looks like it's not triggered by a particular number of riddles. If it's not happening for you, maybe try completing the other side quests.

Here's a map showing the locations of the bodies (1, 3, 5) and the shooter positions (2, 4, 7).

Here is a link to a video that gives a detailed explanation on what to do and where to go. This video belongs to XxOverkillVR