Weapons Murder Presentation + Quiz ~ 83 Slides ~ Guns Knives Blunt Force Instruments, ET AL
There is a free poster which goes with this presentation located here:
Below are excerpts from the presentation. The presentation covers just about every murder weapon. It is highly visual with accompanying text throughout. Actual cases, crime scenes, forensic testing and verdicts are also included. There is also a 20 point multiple choice quiz at the end with an answer key.
I am a retired lawyer, instructor and textbook writer.
~Guns are listed as the Number 1 murder weapon in America by the FBI. Tables of its statistics are at the end of this presentation.
~Handguns lead followed distantly by shotguns and then rifles.
~Gun proponents dispute the FBI’s figures and their arguments are posted online. Any search of guns online will bring up a list of their articles. They assert that knives should be in No. 1 position.
~Guns leave important evidence potentially and cases against the accused can be made or lost based on the gun and its ammunition as evidence, along with expert witness testimony.
~Sometimes the gun is never found which will hinder the investigation. If the gun is found, then many expert forensic tests can be performed.
~Crime Scene & Guns: at a minimum, collection of bullet casings, exploration of bullet holes, detection of spatter patterns, and hunting for dropped weapon (may be nearby such as in dumpster).
Technicians not only collect bullets but an area around and containing the bullet is cut out so that the bullet can be removed carefully at the lab. For example, the bullet is embedded in furniture or carpet.
Gunpowder residue: Burning powder particles expectorate and create a pattern on objects closest to the barrel. This pattern varies by how far the weapon is from the target.
Trajectory, ricochet and bullet holes: if many holes are found at a crime scene, sticks are inserted into bullet holes. These indicate direction of the bullet and can triangulate where the shooter was standing, his height and other details. Ricocheting bullets collect trace evidence from where they bounce, which can be collected and analyzed.
Bullet Wounds: The bullet wounds in the body contain evidence about sequence of wounds, distance from which the gun was fired, the velocity and type of bullet, the bullet type, and the caliber of the gun.
Striations on a fired bullet: Every gun barrel is rifled during manufacture. Spiraling grooves and lands leave mirrored markings on the bullet itself. Bullet can be paired to a weapon. Striations identify a type and model of firearm.
Firing pin impressions: Firing pins leave individual marks on the primer at the bottom of each bullet. Alignment, size of impression, and gun’s age determine marks as the pin makes impressions on the primer. Shown, Glock firing pin impression.
Hidden fingerprints: Wiping fingerprints from the gun may not be enough. While loading bullets with bare hands, tiny quantities of salty sweat are deposited. When a bullet is fired, the heat sets the salts from those prints. A chemical reaction with the metal etches the fingerprints permanently into the casing. If the gunman loaded while wearing gloves though, this will not work.
The accused sometimes wounds himself when using a knife as a weapon. Here are the wounds which could be damaging evidence:
~the knife can stop abruptly if it hits bone. The assailant's hand slides forward, with the hand gripping the knife sliding across the blade. This results in a wounded palm.
~the accused may stab himself on the back of his hand if he stabs at the victim with one hand and tries to restrain the victim with his other hand.
~if the knife is deeply lodged in the victim, the accused may have cut himself as he pulled the knife out of the victim. The blade comes in contact with his palm or fingers while he is pulling out the knife
~sloppy knife work, such as glancing blows, being unprepared for defensive maneuvers and outright misses can end up in the accused’s being stabbed. Once the knife is in momentum, its trajectory takes on a life of its own and stabs him instead.
~all of the above generally presupposes someone who has not been trained in hand to hand combat with a knife. It would be unlikely for someone who had such training to make such mistakes.
Evidence Regarding Knives
~DNA Analysis of any DNA bodily substance on knife, most likely blood
~fingerprint analysis of the knife and matching the prints
~blood spatter analysis to investigate how the crime occurred
~expert witness used to testify that wounds caused by a knife and what type of knife caused them and how they occurred.
~knife injuries which were self inflicted are also subject to expert witness testimony.
~tracing knife purchases and linking them to accused is possible but there is no database or registry for buying knives. They do not have serial numbers.
~although expert witness will probably be able to identify knife as the type of knife used, unless there is DNA or fingerprints on the knife, that will be the extent of the ID.
~there is a lot of blood in stabbings. A lot of this blood will hit the accused’s clothing. The victim’s blood on the accused’s recovered clothing is damaging evidence.