Presentation on theme: "1. Firearm weapons are used for attack or defense. 2. Firearms shoot a projectile by the force of the gases resulting from rapid combustion of an explosive."— Presentation transcript:
1. Firearm weapons are used for attack or defense. 2. Firearms shoot a projectile by the force of the gases resulting from rapid combustion of an explosive mixture.
Step 1: The Comparison Process- test fire the firearm into a water tank in the lab. Step 2: Compare the test bullet to the recovered bullet from the crime scene or the victim using a comparison microscope. Step 3: look for an extractor mark, a breech face marking or a firing pin impression to see what was left on the cartridge casing, to link the suspects weapon to the crime.
All cartridge casings have unique marks on them. There are three different types of firearm markings that examiners can use to determine casings fired from the same weapons.
The firing pin is forced into the primer cup located at the rear center of the cartridge- this makes a firing pin impression.
Once the cartridge powder is ignited by the firing pin, the pressure exerts from the chamber, forcing the back of the cartridge case against the breech face of the weapon.
When a semi-automatic pistol is fired the extractor pulls the cartridge from the chamber and ejects it from the pistol.
Many different elements can be studied in the field of firearm analysis with gun shot residue (GSR) left on the clothes or skin of the person who fired the gun. Washing of the body prior to examination can diminish or destroy gunshot residues. Firearm Analysis Specialists can connect gun shot residue to a particular firearm, helping to solve a case.
This case was located in South Braintree, Massachusetts on April 15 th,1920. Nicola Sacco who was 29 and his companion Bartolomeo Vanzetti, 32. They opened fired at helpless victims at the shoe factory. The victims were heaving the payroll boxes into a waiting car. The killers escaped and they were seen as Italian looking. They denied having guns but both were in possession of loaded hand guns that matched the murder weapon.
This case was in 1835 and took place in London, England. The servant of a homeowner was suspected to have shot and killed him. Henry Goddard and a Police Officer found mold marks on the fired projectile. They found a paper patch that had a torn newspaper piece to seal the ball from the gunpowder. The newspaper was linked to the servant because she had the newspaper in her room. Their careful observations and evidence brought the suspect to be guilty.
Instructor Richard N. Ernest has over 30 years experience in this field and has won awards for being a forensic scientist. Richard N. Ernest is a member of many scientific professional organizations and is a Distinguished Lifetime Member & Certified Firearms Examiner of the Association of Firearms & Tool Mark Examiners. He went to the University of Georgia, where he received his Bachelor degree in Science.