Serology

Used more as a screening method to see if there is a need to take a sampling of evidence for DNA

Defined as the examination and analysis of body fluids

Blood, saliva, semen, and urine

Analyze a sample and establish one of the following: 1. The sample is definitely not a certain substance 2. The sample probably is the substance A positive reaction indicates the possibility of X - Important to remember indicates not specific for - Ex. bleach would test positive - It tests for what you’re looking for, but also could be positive for other things as well. It’s probably blood, but because it can react with other things, we cannot say it is definite “Presumptively positive for whatever you are testing for. It is indicating it, but does not mean specifically that it is there.” - It could show positive for blood, but could be bovine or canine

• Required to confirm the analysis • Confirmatory tests cost more than simpler presumptive tests so presumptive tests are often done to see if confirmatory tests are necessary • Usually takes more time as well

Sensitivity Specificity Safety Simplicity

Neat: body fluid in its natural state (not diluted in any way) Ex. Vaginal fluid and saliva with dilute semen

You want a test that tests for what you are testing for. You don’t want one that tests for 30 things, but rather 3.

Can be performed on a crime scene or at a lab

At a crime scene you want to go with less is more

viable

Substrate and environmental conditions may be important considerations (what works well in the lab may be cumbersome in the field)

Used extensively as blood detection reagents because of their good sensitivity Active dye in Hemastix

Benzidines and Derivatives

Constructed by embedding active materials at end of a plastic strip contributes to the safety and ease of use for testing Hemastix is a one step test since both parts of the test are contained in the stick Presumptive Always required to do a positive and negative control before using at a scene

A small unstained portion of whatever you are testing to show that the substance itself is what is making it turn and not a dye coming off the carrier (do not do it on an area not in question)

Triarylmethanes (similar to Phenolphthalein tests)

Phenolphthalein (Kastle-Meyer Reagent), Leucomalachit Green, Leucrystal Violet and Fluorescein Structural variations give rise to their different color reactions and cause the reaction to fluoresce (fluorescein) PhenolphthaLIN (colorless and reduced form of phenolphthalein) + H2O2 Reacts with hemoglobin Always use a (+) control read results immediately very high sensitivity false positives

Take phenoLIN to hydrogen peroxide and it turns pink, it’s a positive But if it turns pink before adding the hydrogen peroxide, it is a compromised test and not valid. Always need to do a control (around once a day is usually good) Wait to make sure there is no reaction

• Moisten swab with distilled H2O • Swab area you want to test • Add drop of ethanol (no color change) - Increases sensitivity of the test • Add a drop of phenolphthalein (should be no color) • Add a drop of h2o2

process by which light is emitted as a product of a chemical reaction; no additional light is required for the reaction to take place (Luminol) First made in 1853 First used in the application FS in 1937 In 1951, Grodsky combined luminol, sodium perborate, sodium carbonate, and distilled water which is the common mixture used today Good because it can be used on really old stains Bluestar is also a type

occurs when a chemical substance is exposed to a particular wavelength of light and light energy is emitted at longer wavelengths Fluorescein - catalytic reaction between the hemoglobin, blood, and oxygen - very good on latent bloodstaines - longer half-life - does not react with bleach

Luminol + Oxidizer → chemiluminescence Reacts to the hemoglobin in the RBC More luminol must be added for further chemilumi to occur Light blue glow - Bleach tends to appear white As you add more luminol, you are diluting the stain though so you have to be careful

Competeter of luminol Fairly new forensic tool (2000) Derivative of luminol Application by atomizing/ light spraying Stringer and longer lasting luminescence than luminol Do not need complete darkness Lasts for a couple days once mixed