TRAJECTORY ANALYSIS Crime Scene Processing Series New Mexico State Police Criminal Investigations Section Crime Scene Team

“Analysis” Any type of analysis that we do is based on the scientific method. The scientific method is a defined process used to resolve complex problems.

Scientific Method Reach a conclusion. Define the problem or question. Collect information/data to resolve the problem. Test the hypothesis. Organize the information. Posit a hypothesis.

Analysis and Crime Scene Reconstruction In working to establish “what happened,” we are attempting to describe a series of events; however, many times we will not be able to determine everything that happened within that series. We can only give the best explanation of the series of events based on the data that is available; and we are always open to revising our analysis when presented with new data.

Reconstruction In Reconstruction, we are trying to put together WHAT happened, not WHY it happened. In Crime Scene Reconstruction, we only document what can be proven empirically. based on observation and experimentation

Trajectory Analysis Analysis of the path of a bullet, while in flight It’s a snapshot in time It demonstrates the relationship between a firearm and the target

Terminology Perforate - to pass all the way through Penetrate - to enter and stay in Primary impact - the first impact Second, third, etc. impacts – impacts after the first

Cautions Bullets travel in curved lines You must consider many things However, we approximate the bullet’s path with a straight line You must consider many things Ricochets Deflections Variations in surfaces Intervening Objects The pitch and yaw of moving vehicles The biomechanics of the human body

Other Cautions Your knowledge of the firearm Height & weight of the Ejection patterns Stippling patterns Powder ammunition loads Height & weight of the Shooter(s) Victim(s) Not all people fire guns the same way Training & experience Furniture & vehicles can be moved

Straight vs. Curved Trajectory True trajectory = CURVED LINE Approximate trajectory = STRAIGHT LINE A bullet’s true flight path is a parabola, or curved line. We approximate the flight path by using a straight line.

(3) Phases of Ballistics Internal External Terminal Internal Ballistics: Inside the firearm External Ballistics: Between the firearm & the target Terminal Ballistics: After the bullet strikes a target

(3) Possible Shooter Position Zones Most Probable Possible, but Awkward Impossible ZONE 1 – Most Probable ZONE 2 – Possible, but Awkward ZONE 3 - Impossible

Forces Acting on a Bullet in Flight Inertia Gravity Friction (air resistance) Yaw

Can Assist in Answering Questions: Number of participants Location of participants Position /orientation of participants Number and types of firearms Direction of bullet paths Sequences of events

Devises used to Visualize a Trajectory Rods/probes - short range Strings - medium range Lasers - long range

Equipment That You Will Need Rods, cones and washers Angle finder Protractors Colored string and eyelets Ribbons / colored post-it notes Tripod

Equipment That You Will Need Tape measures Chalk line & plumb bob Scientific calculator Laser Ladders Cameras

Information You Will Need Approximate location of the shooter(s) Approximate location of the victim(s) Number of shots fired & the sequence Types of weapons & calibers

Two Points of Reference Projectile paths are most accurately determined when the projectile has passed through two or more solid surfaces

Single Point of Reference For a single point, accuracy is dependant upon The nature of the material struck Styrofoam vs clothing The thickness of the material 4” thick foam vs ¼” thick foam

Documenting the Trajectory OVERHEAD DIAGRAM ELEVATION DIAGRAM EXPLODED VIEW DIAGRAM (overhead view with walls folded down)

Collecting Evidence AFTER CHEMICAL TESTING AND PHOTOGRAPHS FINGERPRINT POWDER AND TAPE LIFT DEFECT MIKROSIL CASTING MATERIAL 3-D

At Least Two Points of Reference

DOCUMENTATION OF VEHICLES SQUARING THE VEHICLE CENTER LINE OF VEHICLE A SECOND REFERENCE LINE PARALLEL TO AXIS OF THE VEHICLE - WHEEL HUBS VERTICAL REFERENCE

Entrance & Exit

Side (lateral) Angle

Upward /Downward Angle

Angle

Elevations

ELEVATIONS

POSITIONS

POSITIONS

POSITION OF VICTIMS

CALIBERS

MOVING VEHICLE

DIAGRAM OF VEHICLE

MUZZLE DISTANCE DETERMINATIONS These determinations are only approximations. Some variables that can affect these distances are: The size of the gun The caliber of the gun The amount of powder in the cartridge Some people reload their cartridges Intermediate objects (clothing, etc.)

CONTACT Blast destruction, tearing of the skin or clothing; soot and powder particles mostly on the inside of the garment and/or driven into the wound. The outline of certain parts of the gun (i.e. barrel bushing, front sights) may leave an impression on the skin around the wound The gases from the explosion of the pistol tear the skin and create a ragged entrance wound. A stellate (star shaped) wound is often seen in head shots.

STELLATE WOUND

NEAR CONTACT (1-4 INCHES) Dark soot with dense deposits of unburned and partially burned powder particles are often seen around the bullet hole blast destruction is still possible in clothing and even skin in some cases Tattooing/stippling (unburned gun powder becoming imbedded under the skin) is often seen on the skin

3-6 INCHES FROM THE TARGET Some medium to light gray soot, with a roughly circular pattern, or a distribution of powder particles may be seen around the bullet hole. Stippling is still possible, particularly with dense and/or poorly burning powders.

What do you think this distance might be?

6-24 INCHES FROM THE TARGET No soot is visible There will be a widely dispersed pattern of powder particles, often loosely adhering to the receiving surface A circular pattern of powder can be seen at closer distances, but the circular pattern may become poorly defined to nonexistent at greater distances.

3-4 FEET OR GREATER No soot or circular rings of powder are present Bullet wiping may be present around the margin of the entry side of the bullet hole regardless of range

CONCLUSION THE ADVANTAGE OF PHYSICAL EVIDENCE AT SHOOTING SCENES IS THAT IT CAN BE USED TO SUPPORT OR REFUTE VICTIM(S), SUSPECT(S) AND WITNESS(S) STATEMENTS