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

2. “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.

3. 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.

4. 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.

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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.

11. (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

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

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

14. 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

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

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

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

18. 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

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

20. 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

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

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

27. At Least Two Points of Reference

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

29. Entrance & Exit

30. Side (lateral) Angle

31. Upward /Downward Angle

32. Angle

33. Elevations

34. ELEVATIONS

35. POSITIONS

36. POSITIONS

37. POSITION OF VICTIMS

38. CALIBERS

39. MOVING VEHICLE

40. DIAGRAM OF VEHICLE

42. 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.)

43. 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.

44. STELLATE WOUND

45. 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

46. 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.

47. What do you think this distance might be?

48. 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.

49. 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

50. 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