How to determine where are they  Trajectory can be calculated by finding two reference points along the flight path of the projectile.  if you assume that bullets travel in straight lines, two reference points will define a single line.  An investigator can then assume that the shooter discharged the firearm somewhere along that line.

 Reference points can be bullet holes in an object, such as a wall or a window, or can be a bullet wound on a victim.  Investigators can also use lasers to trace straight-line paths that can help them determine the position of the shooter or shooters.

EXAMPLE 1:  A bullet is found in the upholstery of a car’s front driver’s seat. The bullet first penetrated the car’s front side window and then the seat. The bullet seemed to have come from an apartment building across the street.  However, no one knows from which window or floor the shot was fired.

 To determine the position of a shooter, the distance between the shooter in the building and the bullet hole in the car seat must be determined.  This requires at least two reference points from which to project a line back to the source of the shooter in the building.  To determine the distance between the shooter and hole in the car seat, you set up a direct proportion using the two right triangles.

Example 2:  A victim was shot from a bullet that came through his front car window as shown in figure below.  Witnesses saw a muzzle flash from a nearby building, but were unsure from which floor the flash originated.  The path of trajectory can be determined by using Point 1 (P1), the broken windshield, and Point 2 (P2), the point where the bullet entered the victim’s head.