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5 essential tools for reconstructing the ballistic trajectory of a projectile

A forensics and product expert from Forensics Source weighs in with advice and recommendations on the best tools


The following is paid content sponsored by The Safariland Group.

By PoliceOne BrandFocus Staff

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 of accuracy.

Several tools are needed to reconstruct a crime scene. (Image The Safariland Group)
Several tools are needed to reconstruct a crime scene. (Image The Safariland Group)

Here are five tools that are essential for every investigator as they conduct crime scene reconstruction.

Bright String

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, said Allen Miller, product manager for the Forensics Source brand, The Safariland Group.

Look for kits like the Forensics Source Trajectory String Kit, recommended 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 spool has over 300 feet of string and notched holes on the string port to keep them separated during use and tied down so they won’t unravel during transit.

Select from standard or deluxe configurations. The deluxe version 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.

Trajectory Rods

Trajectory rods are a viable alternative to bright string as they provide the flexibility of different diameters.

Miller noted the most effective trajectory rods are made of aluminum or steel. They are straight and extend to three-foot lengths, as this is optimal for crime scene reconstruction. Longer rods may sag and give unreliable information.

Aluminum and steel far surpass the reliability of wooden dowels or plastic/fiberglass rods.  While less expensive, wood will warp from humidity and moisture and can be deflected under pressure from intermediate targets.

The EVI-PAQ Laser Trajectory Kit offers several of the best trajectory options. The kit includes four co-aligned steel trajectory rods suitable for use on holes produced by .32-caliber weapons and up. For greater flexibility and accuracy, rods and lasers may be connected in succession using the included stainless steel connectors. In addition, .22-caliber rods also are available.

Protractors

Accurately capturing the angles in any crime scene investigation is essential. That’s where protractors come in.

Protractors are used to measure the angles of impact on a surface and 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 laser beam creates a consistent straight line without the possible sag of string, thus increasing accuracy,” Miller said.

Angle Measuring Tool

Another important tool for the crime scene investigator’s toolbox is an angle finder.

An angle finder calculates the projection of the bullet trajectory, the flight of the bullet and the source of its location. Used in conjunction with trajectory kits, investigators can deploy the tool to measure the horizontal and/or vertical impact angles on a target.

Miller said crime scene investigators should invest in the EVI-PAQ Bullet Trajectory Angle Finder. It helps crime scene investigators determine detailed statistics on where the bullet came from and its trajectory in a consistent, accurate way.

He said that when using the tool, it is important that measurements are taken in relation to the plane of the earth, not necessarily the plane of the impact surface.

Laser

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 tool to align with the straightest estimate of flight of the projectile.

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

Both lasers are activated when a steel connector, or a trajectory rod, is screwed into place at its base, preventing accidental activation. Using the two lasers in conjunction with one another, the investigator is provided with the equipment to demonstrate instances where a second shooter or second bullet path might impact or intersect initial evidence.

These five tools can ensure crime scene investigators have the right equipment they need to accurately and confidently recreate an incident.

For more information about these tools, visit www.safariland.com/products/forensics/.

More About the Expert

Allen Miller is the product manager, Forensics Source for The Safariland Group. For 13 years, Miller has been responsible for the development and management of new products and educating customers on the application of forensic products. Prior to joining The Safariland Group, Miller was a senior crime scene analyst for more than 20 years at the Florida Department of Law Enforcement, Jacksonville Regional Crime Laboratory. Throughout his tenure, he provided crime scene processing services to more than 50 agencies in a 14 county area of northeast Florida, including federal, state and local agencies. 

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