Unit 10: Firearms, Ballistics, and Explosives Test

Identify the following active parts of this Ruger.

When slid into place, this button will prevent the gun from firing - 3 (safety) Press this button to drop the magazine out - 12 (magazine release) Pull this back to check the chamber for cartridges - 7 (slide) Spent cartridges will be forced out from this opening - 6 (ejection port)

In the first lesson of this unit, you learned about chemical reactions, auto-ignition temperature, and flash point. Choose all correct statements.

- At auto-ignition temperature, a material can ignite spontaneously. - Heat and light from a fire is the result of energy emitted from breaking and reforming molecular bonds

After a house fire, your partner collected these two pieces of glass and placed them into evidence. She noted that sample A was taken from the bedroom window and likely was caused by a break-in. She also noted that sample B was taken from the living room and the breakage was likely caused by heat. Support or defend her analysis and state your reasons.

She is correct because the curved lines in the first glass sample taken from the bedroom window have curved lines in the edges of the glass, which means that it shattered because of an impact on something. And the absence of the curved lines and the general smoothness to the edges of sample B taken from the living room means that the heat of a fire caused the glass to break. Therefore, my partner is correct in her assumption.

A woman is shot in the ankle from a building 78 feet away. Investigators determine that the wound entered from approximately 11 degrees to parallel. Which floor was the shooter on? The following information will help determine the location of the suspect: First floor window = 4 feet from the ground Second floor window = 14 feet from the ground Third floor window = 24 feet from the ground Fourth floor window = 34 feet from the ground Fifth floor window = 44 feet from the ground Sixth floor window = 54 feet from the ground The shooter was on floor number_____.

2

Judging by the spatter patterns in the image above, predict what the crime scene evidence might likely suggest

Mist pattern from a gunshot wound - B Gravity has acted on droplets, possibly aftermath of blunt force - C Cast off pattern possibly from a knife or fire poker - A

Why is lead styphnate used in the primer space rather than just gunpowder? What is the difference? How does this difference make them work together?

Primer material like lead styphnate is explosive and can be ignited with frictional impact. Gunpowder is more stable and must be ignited with a flash or flame. So because the lead styphnate can be ignited by the frictional impact it can ignite the gunpowder.

You are called to the aftermath of the house fire pictured above. Accelerant is discovered all over the remains of the bed in the upstairs master bedroom. Explain how you would conduct the arson investigation. - What rooms in the house would you examine first? - Which would you examine last? - What type of packaging would you use to store evidence that you suspect might be a source of volatile accelerants? Why? - Which type of instrument would you use to analyze volatile accelerants and what would you expect it to do, specifically?

- I would examine the rooms that are the least burned first in order... - ...then you would most likely end up finding the point of origin in the main bedroom or at a different point of origin - You would store the evidence using airtight containers like new metal paint cans because it is important to keep the container airtight to trap the vapors and if an accelerant was used there would be traces of flammable liquid. - The lab technician would heat the can to release any accelerants that might be present and then they would obtain a sample of the vapors for testing through the GCMS or gas chromatography and mass spectrometry.

Which of the following could indicate a tight contact gunshot wound but not a close contact gunshot wound?

- Muzzle burn - Large areas of jagged tears in skin

Which pieces of evidence can be found in an entrance wound but not an exit wound?

- Soot - Muzzle burn - Carbon monoxide burn - Stippling - Abrasion ring

In this unit, a good deal of time was spent exploring firearms evidence and testing. Select all true statements

- The best place to find gunshot residue on a suspect is the fleshy part between the thumb and index finger. - A sodium rhodizonate test turns pink in the presence of lead. - Striations on bullets are considered individual evidence.

During the investigation of a house fire, you notice the V-shaped smoke pattern that points to the downstairs living room just left of the front door. There, you find a number of ash trays near an old lounge chair. You also find the wood frame alligator skin, exhibit A in the kitchen above the baking cabinet that stores oil and lard, and wood frame alligator skin, exhibit B, in the living room. - Explain where the fire likely started and how you know, - what the alligator skin evidence tells you, and - what the explanation might be for the seemingly conflicting evidence. - Would you suspect arson or other causes? Why?

- The fire--which is likely natural because of the V-shaped pattern--started in the downstairs living room because the V-shaped smoke pattern points to the point of origin. Some explanation: under ordinary occurrences, fire tends to move up and out, which forms a V-shaped or cone-shaped pattern from the point of origin. - The alligator skin--which is a crackle pattern fire investigators look for on the walls, ceilings, and floors--tells me that the fire burned hotter in the kitchen because of the oil and lard, which are known for burning extremely hot, in the baking cabinet. Explanation: the hotter the fire the smaller the alligator scales get. - The ashtrays are most likely the reason why the fire started; someone could have been smoking and missed the ashtray or one of the burning ashes could have landed on the lounge chair and set it on fire. Then the fire must have spread to the kitchen, which would make the oil and lard catch on fire, making the fire hotter in the kitchen than in the living room. - I do not suspect arson because the v-shaped smoke pattern is very strong evidence of the normal circumstances of the fire--and you can see more above what I think happened.

A firearm is found at a crime scene and the position of the hammer, safety, and all fired and unfired ammunition are recorded. The weapon is ready to be made safe for transport. List the next steps you should do to render the firearm safe, and explain why they should be done.

- You should treat all firearms like they are live and loaded. So you should first point the firearm in a safe direction, which means away from anyone (including yourself), in case the gun might miss fire. Then you should start carefully unloading the weapon: - Press the magazine release to drop the magazine out - Make sure the safety is off in order to do step - Rack the slide to check for chambered cartridges or eject them. - Now it is time to package and transport to the lab and make sure to package the magazine, all bullets, and cartridges are packaged separately. Or follow other procedures when needed.

Select all that apply. Arson or accelerant use is typically suspected when the _____.

- fire pattern has multiple origins - fire pattern is ribbon shaped - fire is hot enough to melt steel

Identify the portion of the cartridge that satisfies the condition.

Best place to find fingerprints - 3 (cartridge case) Place where firing pin impressions can be found - 1 (primer) Place where striations can be found - 5 (bullet) Responsible for stippling and soot - 4 (metal jacket)

A construction worker was standing on scaffolding to wash windows when he was shot in the hip approximately 63 feet in the air. The angle of impact was 38 degrees to parallel. Where was the shooter's likely position? A - behind the bushes about 20ft away B- a passing car about 50 feet away C - the tiki cabana about 80 feet away D - A grove of tropical trees about 120 feet away

C - the tiki cabana about 80 feet away

A house is set on fire, and the firefighters are doing their best to extinguish the blaze. As an investigator, what should you do immediately to attempt to catch the arsonist?

Collect personal information from all bystanders.

Where would you likely see severe tearing of skin when discovering a gunshot victim? What is the tearing caused by?

You would see severe tearing of the skin when it is in tight contact with the victim or from an intraoral gunshot (mostly around the jaw). This happens because when a firearm is fired in tight contact with a bony plate like a skull, it causes pressure from the explosive gases to expand and separate the skin from the bone plate, which causes tears in the skin. It is slightly different with intraoral gunshots though because the explosive gases would tear the facial skin around the mouth.

The technical term for an explosion whose outward expansion occurs faster than the speed of sound is called a(n) _____.

detonation