Mrs. Pearson’s First Semester Forensic Science *For those watching by recording, watch for questions on the slides throughout the presentation. 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 Forensic Science II

Machinegun Barbie meets meets Benny “the chimp” Gambino

What do you think?  Guns don’t kill people, people kill people.  What would your opinion about gun control and gun availability laws be if you grew up in a family that hunts for recreation and/or for food?  Picture someone you are close to. How would your opinion be different if your loved one was seriously wounded by careless handling of a firearm? What kinds of laws or regulations would be important to you? What actions would you want taken against the person who did the shooting?

What do you think?  How would your opinion be different if your loved one was seriously wounded by purposeful aggression using a firearm? What kinds of laws or regulations would be important to you? What actions would you want taken against the person who did the shooting?  What if your loved one was the one who did the shooting in the careless situation? What actions would you want taken against them for the shooting?  The purposeful situation?  Why do I ask you these questions?

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

Ballistics the study of projectiles, trajectories, and the effect on the target  Internal ballistics What happens in the weapon What happens in the weapon  External ballistics What happens after the bullet leaves the barrel What happens after the bullet leaves the barrel  Terminal ballistics (wound ballistics) What happens when the bullet hits the target What happens when the bullet hits the target

Components of typical “round”

Sequence of events  Firing pin or striker hits primer  Primer detonation  Ignition/deflagration* of powder  Increase pressure within casing d/t expanding gases  Bullet forced from casing into rifling of barrel  Rifling imparts “spin” as bullet traverses barrel length  Bullet leaves barrel, followed by hot, still- expanding gases (creates muzzle blast and muzzle flash)  * deflagration – rapid burning (NOT explosion) ** Those watching by recording, include in your the first step in the firing sequence.

Primer indentation

Muzzle blast the sound associated with the round being fired

Muzzle flash the light or flame associated with the round being fired

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Physics of recoil  For every action, there is an equal & opposite reaction  Bullet travels forward, case is forced backwards against the breechface or breechblock, causing recoil  In an automatic or semi automatic weapon, this recoil is what drives the action to “cycle”  htm *Those watching by recording, include in your what happened to the individual in the video as a result of recoil.

Mechanics of projectile wounding  Location  Penetration  Temporary wound cavity  Permanent wound cavity  Projectile deformation/fragmentation

Mechanic of projectile wounding  Physical cutting/crushing of tissue Caliber related Caliber related  Kinetically disrupting/stretching tissue that is adjacent to the path of the projectile Low velocity (most handgun rounds) Low velocity (most handgun rounds) High velocity (rifle rounds & shrapnel from explosions) High velocity (rifle rounds & shrapnel from explosions) KE = ½ m x v 2 KE = ½ m x v 2

Permanent & temporary wound cavities

Fragmentation effect

Bullet deformation

Going out with a Bang!  Internal, external, and terminal ballistics can each aid in weapon identification.  Recoil is due to the equal and opposite reaction to a bullet leaving a gun.  Projectile wounding differs based on type of projectile, speed of projectile, and substance being entered.

Questions?