What is that black line doing on the wall during my DWI video?
You will notice that your DWI video will have a black line on the wall behind you. The reason the line is placed there is to determine if there is any swaying on your part. A good DWI video will show a small amount of sway which is normal. The rhomberg, or "head tilt", a non-standardized test by the National Highway Traffic Safety Administration, the group behind the field sobriety tests, is the main that may show any significant sway during the video.