Forensic Chemistry

Forensic Chemistry

Using chemistry to uncover evidence

Sample

What do we have

Blood, hair, urine

Analysis

What is present

Alcohol, Drugs, Poison

Interpret

What does it mean

Concentration, effects, significance

What Does a Forensic Chemist Do

Evidence received —> Examine + document —> Sample prep —> Confirmatory analysis —> interpretation —> Report Findings —> Court testimony

Drug/Powder Evidence Preservation

Prevent contamination and loss

Fire Debris Evidence Preservation

Airtight container

Preserve volatiles

Blood Evidence Preservation

Correct tube and storage conditions

Trace Evidence Preservation

Prevent loss and cross contamination

Laboratory Analysis (Screening To Confirmation)

Unknown —> Presumptive —> Confirmatory Analysis —> Interpretation

Screening

Colour tests

TLC

Immunoassays

Preliminary Spectroscopy

Conformation

GC-MS

LC-MS

FTIR

Raman

Kastle Meyer Test

Tests to see if unknown substance is blood

Collect sample using swap

Apply drop of phenolphalein solution

Apple drop of hydrogen peroxide solution

Pink = Positive

Colourless = Negative

Controlled Drugs and Substance Act (CDSA)

The CDSA regulates activities including possession, trafficking,
production, importation and exportation, with the applicable
provisions depending on the substance and circumstances.

Controlled Substances

Drugs

Cocaine, methamphetamines, cannabis, alcohol

Controlled Substance Analysis

Screen- Presumptive tests —> Colour tests

Separate- Chromatography —> GC / LC

Identify- Confirmatory Analysis —> MS / FTIR / Raman

Controlled Substance Analysis: Presumptive testing

A screening test that suggests
what may be present, but requires confirmatory
testing for identification.

Marquis Test

Tests for Opiated / Amphetamine (Type drugs)

Positive Colour- varies by drug

Scott Test

Tests for cocaine

Positive Colour- Blue

Duquenois–Levine

Tests for Cannabis

Positive Colour- Purple

Fire Debris

Ignitable Liquid

(Used to be called accelerant: an incendiary
material used to intentionally
and deliberately start a fire)

Fire Debris Storage

Required- Glass mason jar with metal cap and ring
(Exception: large items and liquid samples have separate packaging
requirements)
- If alcohols, solvents, or lacquer thinners are suspected → glass mason jars only

Recommended- Fill jar to approximately ¾ full
- Leave headspace for sampling
- Keep the mouth of the jar clean
- Tightly seal the metal lid and ring
- Apply a numbered, tamper-proof security seal
- Place protective netting over the jar
- If there is a noticeable petroleum odor → seal the jar in a nylon bag
- Submit an empty jar for comparison

- Polynet Protective Netting around jar

Fire Debris Analysis

GC-MS (Gas Chromatography Mass Spectrometry)

GC- Separates gas from one another by pushing it through a think tube and using resistance difference in different kinds or gasses

MS- Identifies by ionizing and uses the unique weight and charge to create a unique chemical fingerprint

Trace Evidence

Small Materials transferred during contact

Fiber, glass, paint

Presumptive Tests

A screening test that suggests what may be present but requires conformation

Significance of Paint as Trace Evidence

Paint is often composed of multiple layers

Layers can differ in- Colour

- Thickness

- Sequence

- Chemical Composition

Multiple characteristics can be used to compare questioned and known samples

FTIR (Fourier Transform Infrared Spectroscopy)

1. Infrared Light is directed at sample

2. Chemical bonds absorb specific frequencies of IR light

3. The instrument measures which frequencies were absorbed

4. An IR spectrum is produced (A chemical fingerprint)

(Large dip = Hardener - Little to no Dip = Paint)

Bullet Components

Bullet- Projectile fired from the firearm

Casing- Holds all components together (Usually made of brass)

Powder- Propellent that ignites to propel bullet (Produces gas pressure)

Primer- Small explosive compartment that ignites the gunpowder

Inorganic Gunshot Residue

Primarily associated with primer residues

Microscopic particles

characterized by elemental composition

Tested with SEM-EDS

Organic Gunshot Residue

Organics compounds associated with propellent and primer

includes compounds from explosives, stabilizers and other additives

Analyzed using GC-MS and LC-MS

SEM-EDS (Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy)

SEM- What does the particle look like? (Image)

Magnifies samples hundreds or thousands of times

EDS- What elements are present? (Graph)

Measures X-ray energies to show what elements are present and in what amounts