Forensic Science Unit Five

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Forensic Science Unit Five

• Mrs. Pearsons 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.
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Lesson Objectives

• Understand how ballistics can be used to identify
  weapons

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Unit 5-Ballistics
Forensic Science II
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• Machinegun Barbie
• meets
• Benny the chimp Gambino

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What do you think?

• Guns dont 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?

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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?

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Video
http//www.youtube.com/watch?vWGHCTMTh7TE
Those watching by recording, include in your
email a description of one of the techniques used
in the video.
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Ballisticsthe study of projectiles,
trajectories, and the effect on the target

• Internal ballistics
• What happens in the weapon
• External ballistics
• What happens after the bullet leaves the barrel
• Terminal ballistics (wound ballistics)
• What happens when the bullet hits the target

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Components of typical round
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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
email the first step in the firing sequence.
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Primer indentation
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Muzzle blastthe sound associated with the round
being fired
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Muzzle flashthe light or flame associated with
the round being fired
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• http//www.filmfodder.com/

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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
• http//www.firearmsid.com/A_featurevideo.htm

Those watching by recording, include in your
email what happened to the individual in the
video as a result of recoil.
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http//www.glenbrook.k12.il.us/
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http//www.glenbrook.k12.il.us/
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Mechanics of projectile wounding

• Location
• Penetration
• Temporary wound cavity
• Permanent wound cavity
• Projectile deformation/fragmentation

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Mechanic of projectile wounding

• Physical cutting/crushing of tissue
• Caliber related
• Kinetically disrupting/stretching tissue that is
  adjacent to the path of the projectile
• Low velocity (most handgun rounds)
• High velocity (rifle rounds shrapnel from
  explosions)
• KE ½ m x v2

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Permanent temporary wound cavities
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Fragmentation effect
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Bullet deformation
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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.

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Questions?