Every shooting leaves a physical record. Bullet holes in walls, strikes on vehicles, fragments in furniture and fired cartridge cases on the ground all hold information about where a shooter stood, which way the gun was pointed and in what order events may have happened. Bullet trajectory analysis is the process of reading that record, and when it is done well it can confirm or disprove the stories told by witnesses, officers and defendants.
Speckin Forensics crime scene investigator Robert Walker has reconstructed shooting scenes throughout his career, and he regularly reviews trajectory work done by other agencies. Here is how the process works and what separates a reliable reconstruction from a weak one.
What Is Bullet Trajectory Analysis?
Bullet trajectory analysis determines the path a bullet traveled through space. Because a bullet in flight follows a nearly straight line over the short distances found at most crime scenes, investigators can often trace that path backward from the points where the bullet struck or passed through objects. When a bullet perforates two surfaces, such as the two sides of an interior wall or a car door and seat, those two holes define a line that can be extended toward the area of origin.
Each trajectory is described by two angles. The vertical angle tells you whether the bullet was traveling upward, downward or level. The horizontal angle, sometimes called azimuth, tells you its left to right direction relative to a reference line such as a wall. Together they place the path in three dimensions.
Reading Bullet Holes and Impact Marks
The shape of a bullet defect carries information. A bullet striking a surface straight on tends to leave a round hole, while one striking at an angle leaves an elongated, elliptical defect. The ratio of the width to the length of that ellipse can be used to estimate the angle of impact, using the same basic trigonometry applied in bloodstain analysis. Investigators also look for lead-in marks, bullet wipe, fracture patterns in glass, and the beveling of holes to determine which side a bullet entered from.
Chemical testing can confirm that a defect was caused by a bullet at all. Tests for lead and copper residue around a hole help distinguish bullet holes from other damage, which matters when a scene has older holes or damage from the incident response.
Tools Used in Bullet Trajectory Analysis
Once defects are identified, investigators use trajectory rods inserted through perforating holes, angle finders and protractors to measure the vertical and horizontal angles, and lasers to project the path across a room or outdoor scene. Everything is photographed with and without the rods and lasers in place, and measured to fixed reference points so the scene can be recreated later. Many agencies now add total stations and 3D laser scanners, which capture the entire scene as a measurable point cloud. Aerial imagery from drones can be valuable for outdoor scenes, and Robert holds an FAA Part 107 certification for exactly that kind of documentation.
The Limits Every Reconstruction Must Respect
Good trajectory work is careful about what it cannot say. A trajectory identifies a line, not a point, so it narrows the area where the muzzle could have been rather than pinpointing an exact location. Bullets deflect when they pass through glass, sheet metal, drywall or the human body, so a path measured beyond an intermediate object may not reflect the original direction of fire. Ricochets create their own patterns and rules. Vehicles may have been moved, doors opened and windows lowered after the shooting, and people are rarely standing still.
Fired cartridge case locations are another area where overconfidence causes problems. Ejection patterns vary with the firearm, ammunition, how the gun was held, whether the shooter was moving and what surface the case landed on. Casings also get kicked, stepped on and driven over. They can support a reconstruction but are rarely precise enough to fix a shooter’s position by themselves.
Putting It All Together
A reliable shooting reconstruction brings every source of information together: trajectories, cartridge case and bullet locations, wound paths from the autopsy, gunshot residue and distance findings, bloodstain patterns, video and audio recordings, and witness statements. The goal is not to make the evidence fit a theory, but to see which account of events the physical evidence can support and which it cannot. Where the evidence is ambiguous, an honest reconstruction says so.
Frequently Asked Questions
Can trajectory analysis tell exactly where the shooter stood?
Usually it identifies a zone or line of possible positions. Combining several trajectories, wound paths and other evidence can narrow that zone considerably.
Can a scene be reconstructed after it has been released?
Often yes, using the original photographs, measurements, scans and evidence. If the structure or vehicle still exists, a later site inspection can also be very valuable.
What is the most common error in shooting reconstruction?
Failing to account for deflection, overreading cartridge case locations and poor documentation of measurements are some of the problems that show up most often in case reviews.
Does Speckin Forensics perform independent shooting reconstructions?
Yes. Robert Walker performs independent shooting scene reconstructions and reviews of existing reconstructions for Speckin Forensics clients, using photographs, measurements, scans, reports and site inspections where possible.
Shooting Reconstruction Services at Speckin Forensics
Bullet trajectory analysis is at the center of the crime scene reconstruction services Speckin Forensics provides to attorneys, insurers and agencies across the country. Robert Walker can work from existing photographs, measurements and scans, or visit the scene, vehicle or structure when it is still available. His FAA Part 107 drone certification adds the option of aerial documentation for outdoor scenes.
A trajectory is only as reliable as the evidence around it, so Robert also looks at the gunshot residue and distance findings and, in police cases, the video and physical evidence discussed in our article on officer-involved shooting reconstruction. Pulling those threads together is what turns a set of measurements into a defensible reconstruction.
Why Work With Robert Walker and Speckin Forensics on Shooting Reconstruction
Robert Walker spent twenty years as a Crime Scene Investigator Specialist with the Lee County Sheriff’s Office in Florida, where he processed homicides, officer-involved shootings and other violent crime scenes, and specialized in the re-creation of shooting scenes. He served as Lead Crime Scene Instructor and Range Officer at the Southwest Florida Institute for Public Service and consulted for Florida Gulf Coast University’s Institute for Weapons and Equipment Research. He is the author of three books on crime scene and firearms topics and has given expert testimony in more than 100 cases, including in federal court.
Robert brings both the hands-on experience of a field investigator and the discipline of a teacher who has trained other CSIs how to do this work correctly. He can review an existing reconstruction, perform an independent analysis, and present the results clearly in reports, exhibits and testimony. Learn about our crime scene reconstruction services, view Robert’s profile, or contact Speckin Forensics. Call 954-763-6134 or 517-349-3528.