Soil Evidence
Soil is collected from a suspect's shoe, is this a known or questioned sample
Questioned - we question where the soil came from
You find a paint chip at the crime scene that has four layers - a clear coat, base coat, primer and electrocoat. What is the most likely source of the paint chip?
These are the four layers of vehicle paint
WHy ar windshields made of laminated glass
In a car accident or if the car is hit by road debris, the windshield will be difficult to break through, which protects the driver
Iodine will turn dark blue/purple when added to...
cornstarch (it starch)
You are investigating an unknown powder. You mix the powder with water and use a pH meter to determine it has a pH of 9. Which of these does NOT describe this powder?
a. the powder is basic b. the powder does not interact with water molecules
c. The powder has more OH- than H+ ions d. this is alkaline
B - this powder does not interact with water molecules
How is pollen (found in soil evidence) helpful to an investigation?
Every plant has differently shaped pollen so it can be determined what species made the pollen and when they bloom, providing clues about location and time of year the crime was committed
Mr. Victim's from door was broken into. Describe how to collect a known sample from the door to match with the potential tools in evidence.
A glass maker wants to make blue glass that breaks into tiny pieces. How can he do this?
Using a manufacturing process that makes it tempered glass and adding the element (cobalt) to make it blue
What is the difference between a confirmation test and a screening test for powders
Confirmation tests determine the exact chemical composition of a powder, while the screening tests (performed first) offer a general idea of the type of powder
<Include Picture> Observe the Becke line of this glass under a microscope. Does the glass, or liquid have a higher Refractive Index? Or is the RI the same
The Becke line will always be on the side of the RI - so the liquid in this case
The line disappears if the RI of the glass and the liquid is the same.
In what soil layer is most organic material found
Top layer - top soil
Consider the four components of paint. Acrylic and Latex are two types of paint _____ while water is a common paint _______ pigment gives paint its ______.
Binder, solvent and color
What type of glass is a car's windshield made out of?
Laminated
You mix a powder with vinegar (an acid) and it bubbles! This means you have what type of powder?
A carbonate powder (ex: baking soda or chalk)
Describe the only circumstance that paint or glass evidence can be individual
When a questioned chip of paint (or glass) physically fits together with a known chip of paint (or glass), like a puzzle
What color is soil that has a high amount of iron
Iron makes the soil red
A paint chip collected from the window sill of a house break is compared to paint chip collected from the suspect's shoe. Both chips have the same number of layers, and the same color of layers. They are placed into test tubes with acetone. The crime scene chip curls, while the suspect's chip does not change. What can you conclude about the samples and whether more testing is needed.
The suspect's chip did NOT come from the window sill of the house break-in - no more testing is needed
Which fracture line is used to determine the direction of impact? From which direction did the impact come.
Radial fractures (A) show direction of impact - ridge lines form right angles to the red rise of the impact.
A known and questioned sample are analyzed using 10 different tests. They have the same characteristics for 9 of the 10 tests. What can you conclude?
If there is even one difference, the two samples are not from the same source
Which type of evidence is most chemically complex?
Paint evidence
You are examining a soil and determine it is aerated, what does this mean
This means the soil contains a high amount of air/oxygen
What are two negatives of using pyrolysis gas chromatography for identifying paint samples? What is one good reason to use pyrolysis gas chromatography?
Negative - It is expensive and destroys the paint sample
Positive - It provides the most accurate and precise results and determines the exact chemical composition
You are at the scene of a hit and run. The victim's car has two broken windows on the passenger side. Describe how to collect known glass sample(s) at the scene: how much, from where, into what type of evidence container.
Take glass directly from each of the broken windows( not from the ground near the windows), 20-50 pieces from each window, packaged separately in rigid containers.
You add a powder to water and measure the pH. It is basic (alkaline) - describe the relative percentage of Oh- an d H+ ions in the powder/water solution.
In alkaline solutions, the OH- ions outnumber the H+ ions because the powder has attached itself to H+ ions
What is Sheila's dogs name?
Huck