forsneic testing

Arson and explosives

Investigation and analysis of fires and explosive events

Combustion

Self-sustaining exothermic oxidation reaction

Explosives

Substances that combine a fuel and an oxidant to release energy rapidly

Gunpowder history

Invented in China around 900 CE

Nitroglycerin

Invented in 1846 by reacting glycerin with nitric acid; highly unstable and shock sensitive but used for blasting and medicinally

Dynamite

Invented by Alfred Nobel in 1867 as a safer form of nitroglycerin mixed with diatomaceous earth or sawdust

Nitrocellulose

Basis of most smokeless firearm propellants

TNT

Initially developed as a yellow dye before use as an explosive

ANFO

Ammonium nitrate mixed with fuel oil; accounts for about 80% of industrial explosives

Low explosive

Deflagrates slower than the speed of sound and requires containment to create explosive force

High explosive

Detonates faster than the speed of sound creating a shockwave

Primary explosive

Extremely sensitive to heat, shock, or friction and used as detonators

Secondary explosive

Less sensitive explosive used as the main charge

Indicator of arson

Multiple apparent points of origin

Butterfly effect (fire behavior)

Small changes in a deterministic system can cause large unpredictable outcomes

Flashover

When an enclosed space ignites simultaneously due to heated combustion gases

Headspace gas chromatography

Technique used to detect volatile components in fire debris

Explosives detection methods

GC-MS, LC-MS, and ion mobility spectroscopy

Ion mobility spectroscopy

Detects explosives based on ion movement in an electric field

Schedule I drugs examples

Heroin, LSD, marijuana

Shear and drag marks on primer

True—they provide clues about firearm action type

Lands

Raised ridges inside a firearm barrel

DNA nucleotide backbone

Sugars and phosphates

Blood alcohol measurement (blood)

Headspace gas chromatography

DNA duplication process

Polymerase chain reaction (PCR)

STR profiling separation method

Gel electrophoresis

Common reaction in presumptive stain tests

Oxidation

Chemical fingerprinting technologies

Mass spectrometry and infrared absorption spectroscopy

Breath alcohol testing technologies

Electrochemical fuel cells and infrared absorption

Drug analysis in blood technologies

Gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry

Breath-to-blood alcohol ratio

Alcohol concentration in breath is about 2100 times lower than in blood

Chromatography purpose

Primarily used for separation but can aid identification

Gel electrophoresis basis

Separation by fragment length

Test to determine if blood is human

Precipitin test

Presumptive blood tests

Kastle-Meyer, luminol, phenolphthalein

Presumptive semen tests

P30 immunoassay, acid phosphatase, ultraviolet light

DNA replication for analysis

Polymerase chain reaction

Minimum cells for DNA profile

Approximately 18 cells

Breath alcohol device technologies

Infrared absorption and electrochemical fuel cells

Most widely used blood alcohol method

Gas chromatography

Gel electrophoresis - separate dna based on size