Crime Scene Processing SeriesCrime Scene Processing Series

TRAJECTORY TRAJECTORY ANALYSISANALYSIS

New Mexico State PoliceNew Mexico State PoliceCriminal Investigations SectionCriminal Investigations Section

Crime Scene TeamCrime Scene Team

““Analysis”Analysis” Any type of analysis that we Any type of analysis that we

do is based on the scientific do is based on the scientific method.method.

The scientific method is a The scientific method is a defined process used to defined process used to resolve complex problems.resolve complex problems.

Define the problem or question.

Collect information/data

to resolve the problem.

Posit a hypothesis.

Reach a conclusion.

Test the hypothesis.

Organize the information.

Scientific MethodScientific Method

Analysis and Crime Scene Analysis and Crime Scene ReconstructionReconstruction

In working to establish “what In working to establish “what happened,” we are attempting to happened,” we are attempting to describe a series of events; however, describe a series of events; however, many times we will not be able to many times we will not be able to determine everything that happened determine everything that happened within that series. within that series.

We can only give the best explanation of We can only give the best explanation of the series of events based on the data the series of events based on the data that is available; and we are always that is available; and we are always open to revising our analysis when open to revising our analysis when presented with new data.presented with new data.

ReconstructionReconstruction In Reconstruction, we are trying In Reconstruction, we are trying

to put together to put together WHAT WHAT happened, not WHY it happened.happened, not WHY it happened.

In Crime Scene Reconstruction, In Crime Scene Reconstruction, we only document what can be we only document what can be proven empirically.proven empirically.

based on observation and based on observation and experimentationexperimentation

Trajectory AnalysisTrajectory Analysis

Analysis of the path of a bullet, while Analysis of the path of a bullet, while in flightin flight

It’s a snapshot in timeIt’s a snapshot in time It demonstrates the relationship It demonstrates the relationship

between a firearm and the targetbetween a firearm and the target

TerminologyTerminology

Perforate - to pass all the way Perforate - to pass all the way throughthrough

Penetrate - to enter and stay inPenetrate - to enter and stay in Primary impact - the first impactPrimary impact - the first impact Second, third, etc. impacts – impacts Second, third, etc. impacts – impacts

after the firstafter the first

CautionsCautions

Bullets travel in curved linesBullets travel in curved lines However, we approximate the bullet’s However, we approximate the bullet’s

path with a straight linepath with a straight line You must consider many thingsYou must consider many things

RicochetsRicochets DeflectionsDeflections Variations in surfacesVariations in surfaces Intervening ObjectsIntervening Objects The pitch and yaw of moving vehiclesThe pitch and yaw of moving vehicles The biomechanics of the human bodyThe biomechanics of the human body

Other CautionsOther Cautions

Your knowledge of the firearmYour knowledge of the firearm Ejection patternsEjection patterns Stippling patternsStippling patterns Powder ammunition loadsPowder ammunition loads

Height & weight of theHeight & weight of the Shooter(s)Shooter(s) Victim(s)Victim(s)

Not all people fire guns the same Not all people fire guns the same wayway Training & experienceTraining & experience

Furniture & vehicles can be movedFurniture & vehicles can be moved

True trajectory = CURVED LINE

Approximate trajectory = STRAIGHT LINE

Straight vs. Curved Straight vs. Curved Trajectory Trajectory

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(3) Phases of Ballistics

Internal External Terminal

1. Internal Ballistics: Inside the firearm

2. External Ballistics: Between the firearm & the target

3. Terminal Ballistics: After the bullet strikes a target

(3) Possible Shooter (3) Possible Shooter Position ZonesPosition 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 Forces Acting on a Bullet in FlightFlight

Inertia Inertia GravityGravity

Friction (air Friction (air resistance)resistance)

Yaw Yaw

Can Assist in Answering Can Assist in Answering Questions:Questions:

Number of participantsNumber of participants Location of participantsLocation of participants Position /orientation of participantsPosition /orientation of participants Number and types of firearmsNumber and types of firearms Direction of bullet pathsDirection of bullet paths Sequences of eventsSequences of events

Devises used to Visualize a Devises used to Visualize a TrajectoryTrajectory

Rods/probes - short range Rods/probes - short range Strings - medium rangeStrings - medium range Lasers - long rangeLasers - long range

Equipment That You Will Equipment That You Will NeedNeed

Rods, cones and washersRods, cones and washers Angle finderAngle finder ProtractorsProtractors Colored string and eyeletsColored string and eyelets Ribbons / colored post-it notesRibbons / colored post-it notes TripodTripod

Equipment That You Will Equipment That You Will NeedNeed

Tape measuresTape measures Chalk line & plumb bobChalk line & plumb bob Scientific calculatorScientific calculator LaserLaser LaddersLadders CamerasCameras

Information You Will Information You Will NeedNeed

Approximate location of the shooter(s)

Approximate location of the Approximate location of the victim(s)victim(s)

Number of shots fired & the Number of shots fired & the sequencesequence

Types of weapons & calibersTypes of weapons & calibers

Two Points of ReferenceTwo Points of Reference

Projectile paths are most accurately Projectile paths are most accurately determined when the projectile has determined when the projectile has passed passed through two or more solid through two or more solid surfacessurfaces

Single Point of ReferenceSingle Point of Reference

For a For a single pointsingle point, accuracy is , accuracy is dependant upondependant upon The nature of the material struckThe nature of the material struck

Styrofoam vs clothing Styrofoam vs clothing The thickness of the material The thickness of the material

4” thick foam vs ¼” thick foam 4” thick foam vs ¼” thick foam

Documenting the Documenting the TrajectoryTrajectory

OVERHEAD DIAGRAMOVERHEAD DIAGRAM ELEVATION DIAGRAMELEVATION DIAGRAM EXPLODED VIEW DIAGRAM EXPLODED VIEW DIAGRAM

(overhead view with walls folded (overhead view with walls folded down)down)

Collecting EvidenceCollecting Evidence

AFTER CHEMICAL TESTING AND AFTER CHEMICAL TESTING AND PHOTOGRAPHSPHOTOGRAPHS

FINGERPRINT POWDER AND TAPE FINGERPRINT POWDER AND TAPE LIFT DEFECTLIFT DEFECT

MIKROSIL CASTING MATERIAL 3-DMIKROSIL CASTING MATERIAL 3-D

At Least Two Points of At Least Two Points of ReferenceReference

DOCUMENTATION OF DOCUMENTATION OF VEHICLESVEHICLES

SQUARING THE VEHICLESQUARING THE VEHICLE CENTER LINE OF VEHICLECENTER LINE OF VEHICLE A SECOND REFERENCE LINE A SECOND REFERENCE LINE

PARALLEL TO AXIS OF THE PARALLEL TO AXIS OF THE VEHICLE - WHEEL HUBSVEHICLE - WHEEL HUBS

VERTICAL REFERENCEVERTICAL REFERENCE

Entrance & ExitEntrance & Exit

Side (lateral) AngleSide (lateral) Angle

Upward /Downward AngleUpward /Downward Angle

AngleAngle

ElevationsElevations

ELEVATIONSELEVATIONS

POSITIONSPOSITIONS

POSITIONSPOSITIONS

POSITION OF POSITION OF VICTIMSVICTIMS

CALIBERSCALIBERS

MOVING VEHICLEMOVING VEHICLE

DIAGRAM OF DIAGRAM OF VEHICLEVEHICLE

MUZZLE DISTANCE MUZZLE DISTANCE DETERMINATIONSDETERMINATIONS

These determinations are only These determinations are only approximations.approximations.

Some variables that can affect these Some variables that can affect these distances are:distances are: The size of the gunThe size of the gun The caliber of the gunThe caliber of the gun The amount of powder in the cartridgeThe amount of powder in the cartridge

Some people reload their cartridgesSome people reload their cartridges Intermediate objects (clothing, etc.)Intermediate objects (clothing, etc.)

CONTACTCONTACT Blast destruction, tearing of the skin or Blast destruction, tearing of the skin or

clothing; soot and powder particles mostly clothing; soot and powder particles mostly on the inside of the garment and/or driven on the inside of the garment and/or driven into the wound.into the wound.

The outline of certain parts of the gun (i.e. The outline of certain parts of the gun (i.e. barrel bushing, front sights) may leave an barrel bushing, front sights) may leave an impression on the skin around the woundimpression on the skin around the wound

The gases from the explosion of the pistol The gases from the explosion of the pistol tear the skin and create a ragged entrance tear the skin and create a ragged entrance wound.wound.

A stellate (star shaped) wound is often A stellate (star shaped) wound is often seen in head shots.seen in head shots.

STELLATE WOUNDSTELLATE WOUND

NEAR CONTACT (1-4 NEAR CONTACT (1-4 INCHES)INCHES)

Dark soot with dense deposits of Dark soot with dense deposits of unburned and partially burned unburned and partially burned powder particles are often seen powder particles are often seen around the bullet hole around the bullet hole

blast destruction is still possible in blast destruction is still possible in clothing and even skin in some cases clothing and even skin in some cases

Tattooing/stippling (unburned gun Tattooing/stippling (unburned gun powder becoming imbedded under powder becoming imbedded under the skin) is often seen on the skinthe skin) is often seen on the skin

3-6 INCHES FROM THE 3-6 INCHES FROM THE TARGETTARGET

Some medium to light gray soot, Some medium to light gray soot, with a roughly circular pattern, or a with a roughly circular pattern, or a distribution of powder particles may distribution of powder particles may be seen around the bullet hole. be seen around the bullet hole.

Stippling is still possible, Stippling is still possible, particularly with dense and/or poorly particularly with dense and/or poorly burning powders.burning powders.

What do you think this What do you think this distance might be?distance might be?

6-24 INCHES FROM THE 6-24 INCHES FROM THE TARGETTARGET

No soot is visibleNo soot is visible There will be a widely dispersed pattern There will be a widely dispersed pattern

of powder particles, often loosely of powder particles, often loosely adhering to the receiving surfaceadhering to the receiving surface

A circular pattern of powder can be seen A circular pattern of powder can be seen at closer distances, but the circular at closer distances, but the circular pattern may become poorly defined to pattern may become poorly defined to nonexistent at greater distances. nonexistent at greater distances.

3-4 FEET OR GREATER3-4 FEET OR GREATER

No soot or circular rings of No soot or circular rings of powder are presentpowder are present

Bullet wiping may be present Bullet wiping may be present around the margin of the entry around the margin of the entry side of the bullet hole regardless side of the bullet hole regardless of rangeof range

CONCLUSIONCONCLUSION

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