Tag Archives: forensic source



Reconstructing a crime scene to gather solid evidence is all about having the right tools. To identify, mark, photograph and measure the ballistic trajectory of a projectile within +/- 5 degrees, choose products known for their quality and accuracy. Allen Miller explains the significant details of these five essentials in the trajectory reconstruction toolkit.



Used to measure the trajectory of a projectile, bright string should be distinct and bright enough to photograph well and strong enough to withstand the pull necessary to show a straight path.

Look for kits like the Forensics Source Trajectory String Kit, recommends Miller, which contains a set of brightly colored red, yellow, blue and pink nylon string spools in a hard plastic insert with spool separators. Each with over 300 feet of string per spool, and notched holes on the string port to keep them separated during use, they can be tied down so they won’t unravel during transit.

Select from standard or deluxe configurations. The deluxe version, Miller notes, includes an additional 150 foot (45 m) spool of special reflective string which is ideal for outdoor night scenes as it reflects bright white when photo-flashed or illuminated with a flashlight.



As a viable alternative to bright string, trajectory rods are used in close quarters or when shorter trajectories are being determined. Offered in different diameters, they facilitate a precise reproduction of a projectile’s path and can be used in conjunction with a laser to afford greater accuracy over a large expanse.

Miller asserts aluminum or steel as the most accurate and effective trajectory rods. They can be connected in succession to three foot lengths using the included stainless steel connectors and maintain their rigidity over the distance.

Fiberglass trajectory rods are another standard in the ballistic trajectory toolkit with various options available. Lightweight yet preserving strength and durability, they are extremely versatile. The multiple colors aid in identifying multiple bullet paths, they can be centered in larger holes with spacer cones, and with the different tips (points or solid) can be used as penetration rods. Miller suggests the Multi-Color Forensic Rod Kit and the 48″ Fiberglass Trajectory Rods both as practical choices.



Accurately capturing the angles in any crime scene investigation is essential and this is where protractors come in.

Used to measure the angles of impact on a surface, protractors enable the zero line to be placed directly next to the evidence for accurate measurements.

A half protractor is ideal for placing in corners or other tight spots that are inaccessible to standard protractors. It features two built-in rulers, a six-inch ruler on the perpendicular base and a three-inch ruler on the face of the protractor. Measurements start at the bottom edge of the protractor, so accuracy is from the ground up.

Miller’s other recommended tool is a protractor with a laser mount. This 12-inch protractor has an adjustable arm which slides from 10 degrees to 170 degrees and can be locked into place once the correct angle is determined.

“The protractor ensures the measurements are accurate while the laser beam creates a consistent straight line without the possible sag of string,” Miller advises.



Another must-have tool for the crime scene investigator’s toolbox, an angle finder is used to calculate the projection of a bullet’s trajectory, the flight of the bullet and ultimately, its source.

Miller recommends crime scene investigators invest in the EVI-PAQ® Bullet Trajectory Angle Finder. Used in conjunction with trajectory kits, investigators deploy the tool to measure the horizontal and/or vertical impact angles on a target. This information helps determine detailed, accurate statistics on where a bullet came from and its trajectory.

He also notes, when using the tool, it is important to measure in relation to the plane of the earth, not the plane of the impact surface.



A laser is used to project the flight of the projectile, either toward an impact surface or away from it, and is the most essential alignment tool to estimate a straight line of flight of a projectile.

The two best lasers on the market are the BP-1 Red Laser Trajectory Pointer and the BP-2 Green Trajectory Laser (built to the same exact standards as the more traditional red). Miller highlights that both lasers are co-aligned with their cases for consistent accuracy when conducting trajectory reconstructions, so the lasers do not deviate from their path.

Activation occurs when a steel connector or a trajectory rod is screwed into the base of the laser thus preventing accidental activation. Using both the laser and the trajectory rods in conjunction often will afford the investigator additional perspectives. For example, to demonstrate instances where a second shooter or second bullet path might impact or intersect initial evidence.



Several kits are available to augment the crime scene investigator’s professional toolkit.

The EVI-PAQ® Laser Trajectory Kit is the most comprehensive option. The kit includes a choice of red or green laser trajectory pointers, tripod mount, four co-aligned steel trajectory rods suitable for use on holes produced by .32-caliber weapons and up. As well, connectors, spacer cones, O-rings and an angle finder round out the kit in a specially designed carry case and provide all the necessities for the reconstruction of ballistic trajectories. .22-caliber rods also can also be purchased.

EVI-PAQ® Standard Trajectory Kit provides the essentials without the laser option. Like the kit above, it contains a tripod mount, four co-aligned steel trajectory rods suitable for use on holes produced by .32-caliber weapons, connectors, spacer cones, O-rings and an angle finder. EVI-PAQ® Trajectory Kit Carrying Cases can be ordered separately.

About the contributor

T. Allen Miller

For more than 30 years, T. Allen Miller has been in the forensics industry. As the Forensics Product Manager for The Safariland Group for more than 15 years, he has been responsible for the development and management of new products and educating customers on the application of forensic products across the country. Prior to joining The Safariland Group, Miller was a senior crime scene analyst for over 20 years at the Florida Department of Law Enforcement, Jacksonville Regional Crime Laboratory and provided crime scene processing services to more than 50 agencies in a 14 county area of Northeast Florida, including federal, state and local agencies.