Firearms + Toolmarks

Question 1

Impacted vs. Striated marks

Answer 1

impacted: hit with something then impression
striated: scratched with something then impression left

Question 2

class characteristics in toolmarks

Answer 2

size and shape

Question 3

what are sub-class marks

Answer 3

irregularities in manufacturing process

Question 4

individual characteristics of toolmarks

Answer 4

incidental marks: lifetime, wear, tear
RACs: randomly acquired characteristics

Question 5

why can we not recreate the toolmark in the lab

Answer 5

many factors we don’t know of like force, angle and if it was two-handed

Question 5

how do we collect toolmark evidence

Answer 5

1. photograph and record info about it
2. submit object if possible if not make an impression
3. comparison microscope

Question 6

presumptive vs. confirmatory test

Answer 6

presumptive: to easily and cheaply detect if it is present
confirmatory: to test for GSR specifically

Question 6

3D imaging

Answer 6

new upcoming, very useful but takes too long to do everything

Question 7

gunshot residue presumptive test

Answer 7

Na Rhodizonate test: tests for lead in generally (could be false) and helps visualize on dark clothing

Question 8

what is a bullet wipe

Answer 8

when the bullet goes into a fabric it will leave a ring of dirt at entrance (it was on the bullet)

Question 9

what is shape that GSR flies in

Answer 9

conical shape if closer than 3ft then GSR will be present on the target and any other objects

Question 10

what is so helpful about the GSR residue

Answer 10

it will help determine the position and distance of shooter

Question 11

what is GSR made of

Answer 11

melted together propellant + primer + bullet pieces aerosol

Question 12

what is blow back

Answer 12

where the primer is pushed back onto the hand

Question 13

where can you find primer on the suspect

Answer 13

you can find it on the webbing of the thumb and the back of your hand

Question 14

what do you look for in primer

Answer 14

you mainly look for barium, lead and antimony that is fused together in a circular ball

Question 15

you can collect by

Answer 15

adhesive stub samples

Question 16

how big is the primer ball

Answer 16

it is 0.1-10 um

Question 17

how do you examine GSR and primer residue

Answer 17

by looking at the shape and element components

Question 18

GSR analysis is limited because

Answer 18

of contamination

Question 19

conclusions of GSR test

Answer 19

1. fired the firearm
2. near firearm
3. handled a newly fired firearm

Question 20

what is the drawback effect

Answer 20

where blood form a close up target is blown back into the barrel

Question 21

where is the drawback effect seen most

Answer 21

suicides

Question 22

3D printed gun

Answer 22

they have lower velocities, the bullet faced the wrong way, and the trajectory was hard to predict