ALS/Chemical Enhancement

Purpose of ALS/chemical enhancement

to locate stains/impressions, to make stains/impressions more visible in photographs, to enrich the details of a stain/impression that may require a comparison

light exists as both a

wave and a particle (photon)

visible light is the portion of the __ that we can visualize as colors

electromagnetic spectrum

light is measured by the

length of its wave in nanometers

1 nm is

1 billionth of a meter

wavelength is measured

peak to peak

the lower the wavelength, the

greater the energy level

the greater the radiant energy, the

greater the penetration

X-ray radiation penetrates

living tissue and can cause cancer

mid-range UV from sunlight causes

sunburn

white light and heat are not

considered harmful

White objects __ all light, while black objects __ all light

reflect, absorb

light can be converted from one wavelength to another, which is known as

luminescence

fluorescence means that the wavelength of light is converted while

exposed to an active energy source like ALS

phosphorescence means that the converted wavelength

continues after the removal of the energy source

With an ALS, some energy is

reflected and some is absorbed

With an ALS, the absorbed light energy

excites e- in an object

In an ALS, as the e- restabilize, they

release energy as light at a different wavelength than the original

Using a barrier filter, the original wavelength is

eliminated allowing only the converted wavelength to be viewed (fluorescence)

wavelength for shortwave UV

180-254 nm

shortwave UV is also called __ and is good for viewing __

UV B/C, untreated latent prints

shortwave UV is dangerous to

skin and eyes

longwave UV wavelength __ and is also called __

365-415 nm, UV A

Longwave UV is good for

body fluids like semen and saliva which fluoresce green and blood that will look black

the longwave UV light barrier filter

non required, but UV protective goggles are good

Violet/Blue ALS light wv

415-530 nm

Violet/blue is good for

bitemarks, bruises, ninhydrin, fluorescein reactions with latent blood, urine, saliva, semen, many fibers, light colored hairs, fluorescent FP powder

violet/blue ALS uses a __ barrier filter

orange or yellow

Orange/Red wv __ and is good for __ with a __ barrier filter

570-700 nm, inks, red filter

IR/Heat/Thermal wv __ and is good for __

700+ nm, QD exams, blood on dark substrates, help locate bodies and hot spots in fire scenes, detect fresh LP

which body fluids will fluoresce

semen, saliva, urine, breast milk

with an IR filter or UV light, blood __ light, making it appear __, while the substrate will likely __

absorbs all the, black, reflect some of the light back

what wavelengths can be damaging to DNA?

200-400

the three ALSs that work best for most body fluids and its wavelength, barrier filter

polilight, omnichrome, ultralite, 450 nm, orange

important features of an ALS

portable, light intensity, spectra range, and cost

portability considerations

size, weight, battery operated

light intensity considerations

brightness, distance light will travel

spectra range considerations

dif evidence fluoresces at diff wavelengths

cost considerations

btwn 40 to 20k dollars

Can purchase __ as a single wv light

UV and blue lights

The FLS (forensic light source) is often a good option bc it is middle of the road in terms of

price, quality, and spectra range

Photography using ALS

1. photograph in white light first (exam quality if visible)
2. attach appropriate filter to camera lens and turn flash off
3. include the scale and identifier in before and after photos

__ can be very effective at locating latent stains/impressions

oblique white light

Blood enhancement techniques

luminol (bluestar), LCV, DAB, fuchsin acid, amino black

luminol, bluestar reacts with

hemoglobin derivatives

LCV and DAB react with

the peroxidase activity of blood

fuchsin acid and amino black react with

the protein content of blood

chemical enhancement of blood is needed when

blood is diluted, blood is on dark or red substrates, to locate latent blood, or to get better detail on faint or partial impressions

Considerations before using chemical enhancement

1. can the object be collected and transported to the lab intact?
2. does the impression need to be enhanced to render sufficient detail?
3. what method will be used to enhance/collect/document the impression?

what method depends on the

type and color of the substrate and the location

prior to blood enhancement, you should

try white light, try oblique light, photograph and measure, collect the sample for serological/DNA testing, conduct a presumptive test for blood (one that reacts with heme)

stains should be __ before applying any chemicals

dry

Why fix a stain?

want to make sure that the stain isn’t dissolved or washed away

what do we fix stains with?

methanol or 5-sulphosalicylic acid

how do we fix a stain?

spray bottle, wash bottle, or total submersion, wait 30 seconds to 3 mins, allow excess fixative to drain off/dry before proceeding

water based amido black is __ based __ stain that produces a __ when blood is present

water or methanol, protein, dark blue/black

water based amino black is best for

non porous surfaces

water based and methanol based amido black does not react with

latent FP

with water-based amido black, fixative can be __

added directly to the reagent

the stained impression with water based or methanol based Amido black can be lifted with

fingerprint tape or a gel lift

methanol based amido black works best with

porous AND nonporous surfaces

methanol based amido black has __ results than water based amido black

sharper results

methanol based amido black can __ certain substrates like paint or varnish

destroy

methanol based amido black is __ if inhaled

flammable, explosive, hazardous

LCV is a __ solution that turns __ where blood is present

clear, dark violet

LCV is the __ form of crystal violet stain

reduced

LCV is good for

both porous and non-porous surfaces

LCV __ fixative, but __ is still recommended for porous surfaces

already contains, pre-fixing

LCV is a __chemical, reacts with __, and is ____

relatively safe, heme, very sensitive

LCV has minimal __ since the solution is clear, but after exposure to light and oxygen, __

background discoloration, the whole background will color

if necessary, __ can be used after LCV

amido black

stains enhanced with LCV will __

fluoresce under various wavelengths

Diaminobenzidene produce a __ where blood is present and works on __

dark brown, porous and non porous surfaces

DAB however is __, requires __, and will not __

hazardous, hydrogen peroxide, transfer onto a gel lift

Fluorescein reacts with __ and must be viewed __

heme, with an ALS

fluorescein fluoresces __ when viewed under __, using a __ filter

blue-green, 455-485, yellow or orange

fluorescein stains are sprayed with fluorescein followed by

hydrogen peroxide

a __ can be added to fluorescein to make it less __

thickener, runny

Coomassie Blue is a __ stain that dyes blood and other body fluids __

protein, blue-violet

coomassie blue is suitable for __

porous and non-porous surfaces

coomassie blue can have a __ base or __ base

methanol, methanol-water

coomassie blue can be __ or __

flammable, hazardous

stains stained with coomassie blue can be lifted with __

gel lift

Hungarian red is a dye that stains _ __in blood and__ __*, and it is a*__ ___ chemical__

proteins, other body fluids, relatively safe

hungarian red is best for __

non-porous surfaces

hungarian red has the ability to __with__ *and a* __ filter

fluoresce, green light, red filter

the stained impression with hungarian red can be lifted with a __ but the dye will

gel lift, diffuse over the gel surface in time

Hungarian red will fuoresce with __ light at wv __ and the filter used in front of the lens is a __ filter

green, 515-560, red

Crowle’s Double stain is a __ that stains __ in blood and other body fluids

red dye, proteins

Crowle’s double stain is best for __, but has been replaced by __

non-porous surfaces, hungarian red

titanium dioxide is a __ based solution that turns __

methanol-based, bloodstains white

titanium dioxide is best for __, but it is __

non-porous surfaces, flammable/hazardous

luminol produces

chemiluminescence

luminol lasts for

1-2 mins

luminol doesn’t typically react with __, but false positives include __

other body fluids, metals, plant peroxidases, and cleaners

luminol-3-amiophthalhydrazide works better on

porous surfaces as non-porous surfaces can often only be treated once and stains may run

luminol-3-a’s sensitivity is

1:1000 to 1:1 million

luminol-3-a works better on __, and __ interfere with DNA testing

older, dried stains, does not

luminol is used as an investigative tool and should only be used when __

no stains are visible to the naked eye

False positives for luminol are often __ and __, last __ or may have a very long duration, and may appear __

immediate, intense, a few seconds, light green to white to blue-violet