Lecture 22 - Advanced Evidence Types 4

Question 1

where are lightbulb filaments as an evidence type relevant

Answer 1

in automotives - headlamp smashes

can see if
- indicator was on
- brake lights working
- headlights illuminated

Question 2

what are the three types of automotive lightbulbs now

Answer 2

Halogen = most popular, have tungsten filament in a glass tube with a nitrogen/argon mix

LED = cheaper, smaller, energy efficient, dont have filaments

Xenon/High Intensity Discharge = has heavy and identifiable metals

Question 3

how can the filament be used in halogen bulbs in forensic analysis

Answer 3

test whether the lamp was illuminated at time of impact

at ambient temp tungsten in the filament is rigid and brittle but at operating temp it is ductile

it also oxidises when exposed to the atmosphere when at operating temps but not when cold

glass may be fused into the filament upon impact

Question 4

how can we look if tungsten filaments have been oxidised or not

Answer 4

using microscopy

Question 5

how can the presence of infused glass into a filament be examined

Answer 5

using SEM-EDX

Question 6

what can be used to check if the filament in a bulb still works

Answer 6

using a multimeter = done after microscopic analysis

Question 7

how can you tell by looking at a filament if it was on or off upon impact

Answer 7

if off there is no pronounced distortion

if on the filament will appear distorted due to it being hot on impact

Question 8

cars with LED lights do not have filaments so what can be used to tell if lights were on here

Answer 8

any car with LEDs is likely to have an internal computer system so this can be used to see if the lights were on or not

Question 9

what two things can tattoos be used for in forensic science

what is the biggest issue

Answer 9

identification e.g in DVI
tracking the movement of people and animals

human interpretation is the biggest issue here

Question 10

what can we analyse within tattoos to suggest location where it was done

Answer 10

pigments in the dye/ink used

using chemical analyses

Question 11

what techniques can be used to analyse tattoo inks (5)

Answer 11

all microscopic techniques

infrared spectroscopy = organic binders and pigments

raman spectroscopy = inorganic pigments

SEM-EDX or XRF = elemental composition of layers

pyrolysis, GC-MS and microchemical testing

Question 11

what are tattoo pigments made out of (2 types of pigment)

Answer 11

organic or mineral pigments - analyse like make up or paints