Introduction to Laboratory Skills and Practical Forensic Science

Introduction to Laboratory Clinical Skills in Forensic Science

• Course Code: AP0400 – Practical Skills in Forensic Science.

• Key Lecturer: Naomi Richardson MSci, AFHEA, Assistant Professor in Forensic Science.

• Purpose: Proficiency in laboratory skills is fundamental for forensic science students. Successful execution and documentation of lab work are essential for ensuring that work can stand up in a court of law.

• Key Industry Organizations: Forensic laboratories routinely work under quality management systems. Major commercial partners include:

  • Cellmark Forensic Services.
  • Key Forensic Services Limited.
  • eurofins.

Good Laboratory Practice (GLP) and Quality Assurance

• Definition of GLP: Developing basic skills and following standard practices to ensure scientific measurements are consistently accurate.

• Consequence of Poor Practice: Leads to unacceptable errors, which can result in incorrect scientific conclusions and legal ramifications.

• Fundamental Principles of GLP:

  • Adhere strictly to Health and Safety (H&S) guidelines.
  • Maintain accurate, exhaustive records of all actions and observations.
  • Ensure all samples, flasks, and volumetric glassware are clearly labeled.
  • Maintain a clean and tidy workspace.
  • Follow Standard Operating Procedures (SOPs) without deviation.
  • Utilize the correct equipment and laboratory glassware for specific tasks.

Health and Safety (H&S) Legislation and Management

• Primary Legal Framework: The Health and Safety at Work Act 1974 is the overarching legislation for workplace safety in the UK.

• Specific Regulations: The Control of Substances Hazardous to Health (COSHH) Regulations 2002. These mandate legal requirements for risk assessments when using hazardous chemicals or biological agents.

• Regulatory Body: The Health and Safety Executive (HSE) provides guidance via their official website (https://www.hse.gov.uk/coshh/).

• Scale of Hazard Management: A 2021 Environment Agency report indicated that approximately $15,000$ chemical substances are used commercially, necessitating robust identification systems.

• University Responsibility Structure (Northumbria University):

  • School of Geography and Natural Sciences -> Department of Applied Sciences.
  • Biosciences Technical Team Manager: Paul Broom.
  • Technical Specialists:
    • Microscopy and Cytometry: Dawn Bruce ($0.6$ fte) and Debbie Pettitt ($0.4$ fte).
    • NUomics Scientific Officers: Clare McCann and Katerina James.
    • Biochemistry Senior Technician: Rachael Saunders.
    • Microbiology Senior Technicians: Sam Davies and Jonathon Brown.
    • Tissue Culture Senior Technician: Ashleigh Jeffs.
    • Nutrition Senior Technician: Karen Walker.
    • Forensic Science Senior Technician: Alex Mora-Blanco.
    • Synthetic/Analytical Senior Technician: Steve Reed.
    • Additional Technicians: Michael Mulholland, Vivian Truong, Callum Crawford, Bethany Aird, David Kong, Natalie Watson, Toby Beckensall, Zara Ahmad, Ben Dobson, Abbie Matthews, Sonya Hamagareb, Sophie Hutchinson, Matt Reynolds.
    • Apprentices: Ben Memari, Curtis Reid.

Risk Assessment and COSHH Protocols

• Risk Assessment Definition: A systematic identification of hazards and implementation of control measures.

• Components of a Lab Risk Assessment:

  • Identifying substance hazards.
  • Evaluating how the substance will be used.
  • Determining necessary control measures.
  • Identifying who is at risk of exposure.
  • Quantifying the amount and duration of exposure.

• Information Sources: Details on reagents are found in Safety Data Sheets (SDS), which include chemical/physical properties, workplace exposure limits, first aid, and firefighting measures.

• Hazard Pictograms & Activity:

  • Flammable, Explosive, Oxidising, Corrosive.
  • Acute Toxicity, Hazardous to the Environment.
  • Health Hazard, Serious Health Hazard.
  • Gas Under Pressure.

• The Risk Matrix (Likelihood $\times$ Severity):

  • Likelihood ranges from Remote ($1$) to Certain ($6$).
  • Severity ranges from Negligible ($1$) to Multiple Fatalities ($6$).
  • Scoring Outcomes:
    • Score $1$ to $10$: Good laboratory practice required.
    • Score $12$ to $18$: Specific identified control measures must be used.
    • Score $20+$: Trained personnel only may proceed.

Laboratory Note-Taking Standards

• Record Types: Students must use two methods: Practical Records and Forensic Laboratory Notes.

• Contemporaneous Documentation: Notes must be recorded at the time the work is performed, never from memory later.

• Note Requirements: Must be neat, logical, accurate, and record every event and observation.

• Handling Errors: Mistakes should be crossed out with a single line to allow original text to remain legible. No white-out or erasure is permitted.

• Calculations and Workings: All mathematical steps must be recorded to facilitate error tracking.

  • Example mass calculation: $Weight\,of\,vial\,+\,powder\,=\,25.6484\,g$, $Weight\,of\,empty\,vial\,=\,25.3214\,g$, therefore $Weight\,of\,powder\,=\,0.3270\,g$.
  • Example dilution: $V_1 \times C_1 = 25\,mL \times 0.025\,M = 6.25 \times 10^{-3}\,M$.

• Multi-sample Preparation Tip: Utilize tables to record additions to samples. Columns should include Sample ID and volumes for Solutions A, B, C, and D. Cross off each addition as it is made.

Standard Operating Procedures (SOPs)

• Definition: A set of detailed, written instructions designed to achieve uniformity in performance and consistency in results.

• Purpose in Forensic Science: SOPs remove ambiguity and ensure transparency and quality for casework.

• Components of an SOP Document:

  • Unique identifying number and revision tracking.
  • Official sign-off by Quality Assurance (QA) or Management.
  • Title Page, Table of Contents, Amendments, and References.
  • Main Body: Purpose, Scope, Responsibilities, H&S, Method/Procedure, Reporting, and Troubleshooting.

• Competency Testing: Staff are frequently audit-tested against SOPs to ensure they can perform tasks properly each time.

Laboratory Equipment and Glassware

• Balances and Weighing:

  • Select appropriate balance: Use 4-place balances for precision ($0.1\,mg$ or $0.0001\,g$).
  • Leveling: Turn leveling feet until the air bubble is centered in the level indicator circle.
  • Tare: Place empty vessel on pan, wait for stability, and set reading to zero.
  • Contamination Prevention: Never return excess solids to the original container.
  • Potential Errors: Factors like electrostatic materials or hygroscopic (moisture-absorbing) materials can affect accuracy.

• Volumetric Glassware Categories:

  • Beaker: General purpose mixing/holding.
  • Measuring Cylinder: Semi-accurate volume measurement.
  • Volumetric Flask: Used for preparing quantitative standard solutions; calibrated "To Contain" (TC) at $20\,^\circ C$.
  • Conical Flask: Good for swirling/titrations.
  • Burette/Pipette: Used for precise volume transfer.

• Accuracy and Tolerances (Class A vs Class B Flasks):

  • $100\,mL$ Class A Tolerance: $\pm 0.08\,mL$.
  • $100\,mL$ Class B Tolerance: $\pm 0.16\,mL$.
  • $1000\,mL$ Class A Tolerance: $\pm 0.30\,mL$.

• Reading a Meniscus:

  • Always read from the bottom of the concave curve.
  • Avoid Parallax: Ensure eyes are at the same horizontal level as the meniscus.
  • Contrast: Use a white background for clear liquids to better see graduation marks.

• Gilson (Microlitre) Pipettes:

  • Volume Range: 1.0\,̄\,1000\,̄\mu L.
  • Best Practice: "Dial up" the volume, use appropriate tips, keep vertical, and never submerge the pipette body beyond the disposable tip.
  • Calibration: Pipettes must be calibrated before use, and serial numbers must be recorded in lab notes.

Advanced Sample Preparation Techniques

• Centrifugation:

  • Purpose: Separation of particles suspended in liquid (e.g., separating cheek cells from saliva).
  • Components: Rotor assembly, spindle, centrifuge tubes, safety lid, and armored guard ring.

• Vortexing:

  • Purpose: Thorough mixing of mixtures, especially for small sample volumes.
  • Best Practice: Always ensure the container has a lid on before placing it on the vortex mixer to prevent aerosolization or spills.