Forensics: Ballistics Forensics: Ballistics

VocabularyVocabulary1.1. Ballistics – the study of projectiles Ballistics – the study of projectiles

(bullets) and firearms(bullets) and firearms2.2. Barrel – the long, metal tube that Barrel – the long, metal tube that

guides a projectile out of a firearmguides a projectile out of a firearm3.3. Bullet – the projectile that is released Bullet – the projectile that is released

when a firearm is dischargedwhen a firearm is discharged4.4. Caliber – a measure of the inside Caliber – a measure of the inside

diameter of a firearm barreldiameter of a firearm barrel5.5. Cartridge – a case that holds a bullet, Cartridge – a case that holds a bullet,

primer powder, and gunpowderprimer powder, and gunpowder

VocabularyVocabulary6.6. Firearm – a weapon capable of firing a Firearm – a weapon capable of firing a

projectile using a confined explosive as a projectile using a confined explosive as a propellantpropellant

7.7. Fully automatic – a firearm with a clip-fed Fully automatic – a firearm with a clip-fed mechanism that fires repeatedly as long mechanism that fires repeatedly as long as the trigger is pressedas the trigger is pressed

8.8. Gunshot residue (GSR) – the tiny particles Gunshot residue (GSR) – the tiny particles expelled from a firearm when it is firedexpelled from a firearm when it is fired

9.9. Lands and Grooves – the ridges (lands) Lands and Grooves – the ridges (lands) and the depressions (grooves) found on and the depressions (grooves) found on the inside of a firearm’s barrel that are the inside of a firearm’s barrel that are created when the firearm is created when the firearm is manufacturedmanufactured

VocabularyVocabulary10.10. Muzzle – the end of the barrel from Muzzle – the end of the barrel from

which the projectile exits a firearmwhich the projectile exits a firearm11.11. Pistol – a handheld firearmPistol – a handheld firearm12.12. Revolver – a pistol with a revolving Revolver – a pistol with a revolving

cylindercylinder13.13. Rifle – a firearm that has a long Rifle – a firearm that has a long

barrel; a long gunbarrel; a long gun14.14. Rifling – the spiral pattern of lands Rifling – the spiral pattern of lands

and grooves in the barrel of a and grooves in the barrel of a firearmfirearm

VocabularyVocabulary15.15. Semiautomatic – a pistol with a clip-Semiautomatic – a pistol with a clip-

fed mechanism that fires one shot fed mechanism that fires one shot per pull of the trigger; the empty per pull of the trigger; the empty cartridge ejects and the next cartridge ejects and the next cartridge advances automaticallycartridge advances automatically

16.16. Shell casing – the metal (usually Shell casing – the metal (usually brass) housing for the gunpowder of brass) housing for the gunpowder of a firearma firearm

17.17. Trajectory – the path of flight of a Trajectory – the path of flight of a projectile projectile

What we will learnWhat we will learn

The differences between a handgun, a rifle, The differences between a handgun, a rifle, and a shotgunand a shotgun

Distinguishing between a bullet and cartridgeDistinguishing between a bullet and cartridge The rifling on the gun barrel and how it affects The rifling on the gun barrel and how it affects

the flight of a projectilethe flight of a projectile Relationship between barrel size and caliberRelationship between barrel size and caliber How bullets are test-fired and matchedHow bullets are test-fired and matched Role of ballistics recovery and examination at Role of ballistics recovery and examination at

the crime scenethe crime scene Position of the shooter based on bullet Position of the shooter based on bullet

trajectorytrajectory

What questions does ballistics What questions does ballistics help answer at a crime scene?help answer at a crime scene?

What type of firearm was used?What type of firearm was used? What was the caliber of the bullet?What was the caliber of the bullet? How many bullets were fired?How many bullets were fired? Where was the shooter standing?Where was the shooter standing? What was the angle of impact?What was the angle of impact? Has this firearm been used in a Has this firearm been used in a

previous crime?previous crime?

History of FirearmsHistory of Firearms

Chinese invented gunpowderChinese invented gunpowder Potassium nitrate, charcoal, and sulfurPotassium nitrate, charcoal, and sulfur Expands to 6 times original sizeExpands to 6 times original size

14th century – directed explosives down a 14th century – directed explosives down a cylinder and move a deadly projectilecylinder and move a deadly projectile Matchlock weaponsMatchlock weapons Flintlock weaponsFlintlock weapons Muzzle-loadersMuzzle-loaders Breech-loadersBreech-loaders

Firearms in ForensicsFirearms in Forensics

1835 – London, 1835 – London, England. Mold mark England. Mold mark used to make bullet used to make bullet from molten lead used from molten lead used as evidence in as evidence in homicide casehomicide case

1863 – Examination of 1863 – Examination of the bullet type and the bullet type and design used to shoot design used to shoot Gen. Stonewall Jackson Gen. Stonewall Jackson showed he was shot showed he was shot by one of his own men by one of his own men

1879 – Minnesota. 1879 – Minnesota. Rifling marks from a Rifling marks from a revolver used in court revolver used in court to differentiate two to differentiate two revolversrevolvers

1925 – The 1925 – The comparison comparison microscope is microscope is developed by Philip developed by Philip GravelleGravelle

Modern FirearmsModern Firearms

Two basic Two basic TypesTypes

1.1. Long guns – use Long guns – use of two hands for of two hands for accurate firingaccurate firing

2.2. Handguns – Handguns – fired with one fired with one hand (pistols)hand (pistols)

Firearms ContinuedFirearms Continued Long GunsLong Guns

Rifles – fire cartridgesRifles – fire cartridges Shotguns – fire small round Shotguns – fire small round

pellets (shot) or single pellets (shot) or single projectile called slugprojectile called slug

HandgunsHandguns Revolver – cylinder that holds Revolver – cylinder that holds

cartridges turns as it firescartridges turns as it fires Usually Holds up to 6 cartridges in Usually Holds up to 6 cartridges in

the cylinderthe cylinder Semiautomatic – fire only one bullet Semiautomatic – fire only one bullet

per pull of triggerper pull of trigger Holds up to 20 cartridges in a clip Holds up to 20 cartridges in a clip

(magazine)(magazine) Fully Automatic – fire repeatedly as Fully Automatic – fire repeatedly as

long as trigger is pressedlong as trigger is pressed

RiflingRifling Lands and grooves cause bullet to spiral Lands and grooves cause bullet to spiral

when exiting the barrelwhen exiting the barrel Impossible to produce two identically rifled Impossible to produce two identically rifled

gun barrelsgun barrels Barrel marks each bullet with own specific Barrel marks each bullet with own specific

patternpattern

How lands and grooves are How lands and grooves are mademade

Bullets and CartridgesBullets and Cartridges Anatomy of a CartridgeAnatomy of a Cartridge

1.1. Bullet – made of lead, copper, or Bullet – made of lead, copper, or combinationcombination

Can be metal-jacketed, hollow-pointed, plastic-Can be metal-jacketed, hollow-pointed, plastic-coatedcoated

2.2. Primer powder – initiates explosion that Primer powder – initiates explosion that pushes bullet down barrelpushes bullet down barrel

3.3. Anvil and Flash Hole – deliver the Anvil and Flash Hole – deliver the explosive charge from primer powder to explosive charge from primer powder to gun powdergun powder

4.4. Headstamp – on bottom of cartridge Headstamp – on bottom of cartridge casing identifies caliber and manufacturercasing identifies caliber and manufacturer

How a Firearm WorksHow a Firearm Works1.1. Pull the trigger – firing pin hits base of Pull the trigger – firing pin hits base of

cartridge & ignites primer powder cartridge & ignites primer powder mixturemixture

2.2. Tiny explosion of primer powder on anvil Tiny explosion of primer powder on anvil shoots spark through flash hole to shoots spark through flash hole to gunpowder supplygunpowder supply

3.3. Gunpowder ignites & pressure of Gunpowder ignites & pressure of explosion pushes bullet from casing into explosion pushes bullet from casing into barrel of firearm. barrel of firearm.

4.4. Bullet follows lands and grooves pattern Bullet follows lands and grooves pattern of barrel and spirals before leaving the of barrel and spirals before leaving the barrelbarrel

Caliber of the CartridgeCaliber of the Cartridge

Named by caliber and lengthNamed by caliber and length Common calibers: .22,.25,.357,.38,.44,.45Common calibers: .22,.25,.357,.38,.44,.45

Usually measured in hundredths of an inchUsually measured in hundredths of an inch .45 caliber – 45/100 of an inch.45 caliber – 45/100 of an inch European method – metric system (mm)European method – metric system (mm) Caliber also refers to diameter of a barrelCaliber also refers to diameter of a barrel

Caliber of ammunition should match caliber of Caliber of ammunition should match caliber of firearm that shoots itfirearm that shoots it

Bullets and Cartridge Casings Bullets and Cartridge Casings at Crime Scenesat Crime Scenes

Investigators Investigators compare bullets and compare bullets and spent cartridges from spent cartridges from crime scene with crime scene with bullets and spent bullets and spent cartridges from cartridges from suspected weaponsuspected weapon Test-fire weapon into Test-fire weapon into

water tank or gel water tank or gel block to capture bullet block to capture bullet without damaging itwithout damaging it

Compared using Compared using comparison comparison microscopemicroscope

Marks on Spent Cartridge Marks on Spent Cartridge CasingsCasings

Firing pin marks are left on Firing pin marks are left on spent cartridgespent cartridge Also individual to each gunAlso individual to each gun Left on cartridge when firing pin Left on cartridge when firing pin

strikes bottom of cartridge when strikes bottom of cartridge when firearm is shotfirearm is shot

Other markings:Other markings: Breech marksBreech marks Extractor markersExtractor markers Ejector marksEjector marks

*** extractor and ejector do not *** extractor and ejector do not happen in revolverhappen in revolver

Class vs. Individual Class vs. Individual CharacteristicsCharacteristics

What is a class characteristic?What is a class characteristic? The properties that all the members The properties that all the members

of a certain group of objects or of a certain group of objects or substances have in commonsubstances have in common

What is an individual characteristic?What is an individual characteristic? Properties of evidence that can be Properties of evidence that can be

attributed to a common source with attributed to a common source with extremely high degree of certaintyextremely high degree of certainty

Class vs. Individual Class vs. Individual CharacteristicsCharacteristics

of Firearmsof Firearms Class: Class:

Type of gun (long gun, handgun, rifle, Type of gun (long gun, handgun, rifle, shotgun, pistol, revolver)shotgun, pistol, revolver)

Manufacturer (Beretta, Smith & Wesson, Manufacturer (Beretta, Smith & Wesson, Winchester)Winchester)

Caliber Caliber Individual:Individual:

Rifling (lands and grooves)Rifling (lands and grooves) Spent casing markingsSpent casing markings Firing pin marksFiring pin marks

Gunshot Residue (GSR)Gunshot Residue (GSR) Traces of smoke and particles of Traces of smoke and particles of

unburned powder carried sideways unburned powder carried sideways from firearm by expansion of gases as from firearm by expansion of gases as bullet is firedbullet is fired

Contain nitrates – stick to shooter and Contain nitrates – stick to shooter and area firedarea fired

Amount found decreases as distance Amount found decreases as distance between firearm and victim increasesbetween firearm and victim increases

GSR looked for to recreate crime scene GSR looked for to recreate crime scene and find suspect. and find suspect.

DatabasesDatabases Can be searched to match crime-scene Can be searched to match crime-scene

evidence to registered weapons evidence to registered weapons NIBIS (National Integrated Bullet NIBIS (National Integrated Bullet

Identification System) – computer files Identification System) – computer files of ballistic markings used in previous of ballistic markings used in previous crimescrimes

Drugfire – FBI database focuses on Drugfire – FBI database focuses on cartridge casingscartridge casings

2002 – merged to form NIBIN (National 2002 – merged to form NIBIN (National Integrated Ballistics Network) Integrated Ballistics Network)

TrajectoryTrajectory Helps to determine where the Helps to determine where the

shooter was located during a crimeshooter was located during a crime Calculating trajectory – two reference Calculating trajectory – two reference

points along the flight path of points along the flight path of projectile are used to assume that a projectile are used to assume that a shooter discharged firearm shooter discharged firearm somewhere along that linesomewhere along that line ** ignoring gravity** ignoring gravity

Calculating TrajectoryCalculating Trajectory Reference points – bullet holes in an object Reference points – bullet holes in an object

or bullet wound on a victimor bullet wound on a victim Less specific reference points – GSR on Less specific reference points – GSR on

objects, spent cartridge casings.objects, spent cartridge casings. Victim’s body – entrance wound and exit woundVictim’s body – entrance wound and exit wound

Tools such as lasers and repositioning Tools such as lasers and repositioning corpse to position at time of impact are corpse to position at time of impact are helpfulhelpful

**Exceptions** - bullets can ricochet, become **Exceptions** - bullets can ricochet, become damaged and not provide direct pathdamaged and not provide direct path

Gravity and TrajectoryGravity and Trajectory

Two major forces act on Two major forces act on bullet once fired:bullet once fired: Forward force of gunshotForward force of gunshot Downward force of Downward force of

gravitygravity Bullet begins to drop as Bullet begins to drop as

soon as shotsoon as shot farther the shooter – farther the shooter –

greater the effectgreater the effect

Wind speed and Wind speed and direction also effect direction also effect shooter angleshooter angle

Determining the Location of a Determining the Location of a ShooterShooter

Scenario: Bullet is found in upholstery of Scenario: Bullet is found in upholstery of car’s front driver’s seat. Bullet hole is car’s front driver’s seat. Bullet hole is found in front driver side window.found in front driver side window.

Shot seems to have come from a Shot seems to have come from a window in some apartments across the window in some apartments across the street. street.

What are the two reference points to What are the two reference points to predict a path of trajectory?predict a path of trajectory?

bullet in seat, hole in windowbullet in seat, hole in window

Police use a laser to project path Police use a laser to project path

Path of bullet

Horizon

Wind shield

Distance along path of bullet to window, 23.9”

Distance along horizon to window, 23.5”

yx

60 feet

building

Calculation Calculation Which window?Which window?

Distance from car to building: 60 feet or Distance from car to building: 60 feet or 720”720” Distance from window to car seat (along Distance from window to car seat (along

horizon):horizon): 23.5 23.5”” Distance from window to car seat (along Distance from window to car seat (along

bullet path): bullet path): 23.9”23.9” Formula:Formula:Distance to window along bullet pathDistance to window along bullet path = = distance to shooter (x)distance to shooter (x)

Distance to window along horizonDistance to window along horizon distance to buildingdistance to building

Bullet WoundsBullet Wounds Entrance wounds – generally smaller Entrance wounds – generally smaller

because skin is elasticbecause skin is elastic Exit wounds – bigger because bullet may Exit wounds – bigger because bullet may

pick up tissue, bone, etc as it goes through pick up tissue, bone, etc as it goes through bodybody

Clues near body:Clues near body: If bullet penetrates clothing first, fibers may be If bullet penetrates clothing first, fibers may be

imbedded into wound in direction of imbedded into wound in direction of penetrationpenetration

GSR – found around entrance woundsGSR – found around entrance wounds If in contact with skin, hot gases may burn skinIf in contact with skin, hot gases may burn skin

Bullet woundsBullet wounds Fate of a bullet in body:Fate of a bullet in body:

May ricochet off bone and do internal May ricochet off bone and do internal damage before exitingdamage before exiting

May not exit the body at allMay not exit the body at all

Factors that influence fate:Factors that influence fate: High speed – may pass directly High speed – may pass directly

throughthrough Much more likely than low velocityMuch more likely than low velocity Small caliber bullets – more likely to Small caliber bullets – more likely to

be lodgedbe lodged Larger caliber bullets – likely to pass Larger caliber bullets – likely to pass

right throughright through