This page of our game guide to Batman: Arkham Knight contains a description of the crash site investigation scene. Batman must reconstruct the events by using the detective mode.
Approach the car and activate the Scan In Evidence mode. Start from scanning the whole vehicle (always hold the appropriate key/button). From the first reconstruction, you will learn that the driver flew out through the windshield. Start moving the timeline to locate the place where his body landed. Approach the body and scan it.
Return to the vehicle and scan the passenger seat. You will notice that the door on the right side was detached from the vehicle during the crash. Use the timeline again to learn the location of the door. Go to the door and scan it.
Return to the car and start manipulating the timeline. Now, your priority will be to find the place where Barbara landed after she jumped out of the car. Scan this area. Your next discovery will be the fact that someone shot her after she got out of the car.
Again, scan the place where Barbara landed to perform a ballistic test. This operation will tell you that it was Arkham Knight who stopped Barbara from escaping.
At the end, you need to find the trail that Oracle left behind her, after getting out of the car and being caught by Arkham Knight again. The place where the trail begins is shown in the picture above. After moving the timeline to the proper position, you need to examine that wooden box. You will find the scrambler. Talk to Lucius Fox. Also, Alfred will tell you about some side quests available.
Note - you don't have to complete the side quests that Alfred told you about. If you want to stick with the main story, go meet with Lucius.