Mrs. Pearson’s First Semester Forensic Science

*For those watching by recording, watch for questions on the slides throughout the presentation. Email me the answers to the questions within two days of the lesson being presented in order to receive credit for watching the recording.

Understand how ballistics can be used to identify weapons

Unit 5-Ballistics Unit 5-Ballistics

Forensic Science IIForensic Science II

Machinegun BarbieMachinegun Barbie

meetsmeets

Benny “the chimp” GambinoBenny “the chimp” Gambino

What do you think?What do you think? Guns don’t kill people, people kill people.Guns don’t kill people, people kill people. What would your opinion about gun control and What would your opinion about gun control and

gun availability laws be if you grew up in a family gun availability laws be if you grew up in a family that hunts for recreation and/or for food?that hunts for recreation and/or for food?

Picture someone you are close to. How would Picture someone you are close to. How would your opinion be different if your loved one was your opinion be different if your loved one was seriously wounded by careless handling of a seriously wounded by careless handling of a firearm? What kinds of laws or regulations would firearm? What kinds of laws or regulations would be important to you? What actions would you want be important to you? What actions would you want taken against the person who did the shooting?taken against the person who did the shooting?

What do you think?What do you think? How would your opinion be different if your loved one was How would your opinion be different if your loved one was

seriously wounded by purposeful aggression using a seriously wounded by purposeful aggression using a firearm? What kinds of laws or regulations would be firearm? What kinds of laws or regulations would be important to you? What actions would you want taken important to you? What actions would you want taken against the person who did the shooting?against the person who did the shooting?

What if your loved one was the one who did the shooting in What if your loved one was the one who did the shooting in the careless situation? What actions would you want taken the careless situation? What actions would you want taken against them for the shooting? against them for the shooting?

The purposeful situation?The purposeful situation? Why do I ask you these questions?Why do I ask you these questions?

VideoVideo

http://www.youtube.com/watch?v=WGHCTMTh7TE

*Those watching by recording, include in your email a description of one of the techniques used in the video.

BallisticsBallisticsthe study of projectiles, trajectories, and the effect on the targetthe study of projectiles, trajectories, and the effect on the target

Internal ballisticsInternal ballistics What happens in the weaponWhat happens in the weapon

External ballisticsExternal ballistics What happens after the bullet leaves the barrelWhat happens after the bullet leaves the barrel

Terminal ballistics (wound ballistics)Terminal ballistics (wound ballistics) What happens when the bullet hits the targetWhat happens when the bullet hits the target

Components of typical “round”Components of typical “round”

Sequence of eventsSequence of events Firing pin or striker hits primerFiring pin or striker hits primer Primer detonationPrimer detonation Ignition/Ignition/deflagration*deflagration* of powder of powder Increase pressureIncrease pressure within casing d/t expanding within casing d/t expanding

gasesgases Bullet forced from casing into Bullet forced from casing into rifling of barrelrifling of barrel Rifling imparts “spin” as bullet traverses barrel Rifling imparts “spin” as bullet traverses barrel

lengthlength Bullet leaves barrel, followed byBullet leaves barrel, followed by hot, still- hot, still-

expanding gases expanding gases (creates(creates muzzle blast muzzle blast and and muzzle flashmuzzle flash))

* deflagration – rapid burning (NOT explosion)* deflagration – rapid burning (NOT explosion)

**Those watching by recording, include in your email the first step in the firing sequence.

Primer indentationPrimer indentation

Muzzle blastMuzzle blastthe sound associated with the round being firedthe sound associated with the round being fired

Muzzle flashMuzzle flashthe light or flame associated with the round being firedthe light or flame associated with the round being fired

http://www.filmfodder.com/http://www.filmfodder.com/

Physics of recoilPhysics of recoil For every action, there is an equal & For every action, there is an equal &

opposite reactionopposite reaction Bullet travels forward, case is forced Bullet travels forward, case is forced

backwards against the breechface or backwards against the breechface or breechblock, causing recoilbreechblock, causing recoil

In an automatic or semi automatic weapon, In an automatic or semi automatic weapon, this recoil is what drives the action to “cycle”this recoil is what drives the action to “cycle”

http://www.firearmsid.com/http://www.firearmsid.com/A_featurevideo.htmA_featurevideo.htm

*Those watching by recording, include in your email what happened to the individual in the video as a result of recoil.

http://www.glenbrook.k12.il.us/

http://www.glenbrook.k12.il.us/

Mechanics of projectile woundingMechanics of projectile wounding

LocationLocation PenetrationPenetration Temporary wound cavityTemporary wound cavity Permanent wound cavityPermanent wound cavity Projectile deformation/fragmentationProjectile deformation/fragmentation

Mechanic of projectile woundingMechanic of projectile wounding

Physical cutting/crushing of tissuePhysical cutting/crushing of tissue Caliber relatedCaliber related

Kinetically disrupting/stretching tissue that Kinetically disrupting/stretching tissue that is adjacent to the path of the projectileis adjacent to the path of the projectile Low velocity (most handgun rounds)Low velocity (most handgun rounds) High velocity (rifle rounds & shrapnel from High velocity (rifle rounds & shrapnel from

explosions)explosions) KE = ½ m x vKE = ½ m x v22

Permanent & temporary Permanent & temporary wound cavitieswound cavities

Fragmentation effectFragmentation effect

Bullet deformationBullet deformation

Going out with a Bang!Going out with a Bang!

Internal, external, and terminal ballistics Internal, external, and terminal ballistics can each aid in weapon identification.can each aid in weapon identification.

Recoil is due to the equal and opposite Recoil is due to the equal and opposite reaction to a bullet leaving a gun.reaction to a bullet leaving a gun.

Projectile wounding differs based on type Projectile wounding differs based on type of projectile, speed of projectile, and of projectile, speed of projectile, and substance being entered. substance being entered.

Questions?Questions?