The Building Blocks of a Sound Investigation

By Bob Denaro (KPM) @ the BDG Training Team · June 2026

Every investigation is unique, but the foundations are consistent and they apply to any investigator, in any organisation. At the core sits one principle: assume nothing, believe nothing, challenge everything.

The five building blocks

• Professional curiosity — the discipline of asking 'why?' and 'what else might explain this?'

•The 5WH framework — structuring your investigation around Who, What, Where, When, Why and How

• Hypothesis building — developing and testing more than one explanation for what happened

•Gap analysis — knowing what you know, what you don't know, and what that means for your lines of enquiry

•Record keeping — comprehensive, contemporaneous and objective documentation of every decision

The five first priorities in any investigation

Alongside the building blocks, every investigator must consider five immediate priorities at the outset of any case — from a trading standards complaint to a complex counter-fraud investigation.

1. Preserve life

The safety and welfare of any person at risk comes first. Consider whether anyone requires urgent medical attention, safeguarding intervention or protection from ongoing harm.

2. Preserve scenes

Identify and secure any relevant scene without delay. A scene not preserved promptly may be contaminated, altered or lost — taking with it evidence that cannot be recovered.

3. Secure evidence

Physical, documentary and digital evidence must be identified and secured at the earliest opportunity. What exists? Where is it held? What steps prevent loss, destruction or tampering?

4. Victims and witnesses

Identify all victims and witnesses promptly and consider their immediate needs, including safeguarding and vulnerability. Take initial accounts as soon as practicable — memories fade and accounts can be influenced over time.

5. Suspects

Identify the suspect or subject accurately and completely — full name, role, address, associates and relevant intelligence. Consider whether early action is needed to prevent ongoing harm, evidence loss or interference with witnesses.

Training that covers this

These principles are the backbone of BDG's Investigation Essentials programme — see our full range of investigation training courses or email info@bdgtrainingconsultancy.co.uk for a free training consultation.

This article is adapted from the BDG Investigator Bulletin, Edition 3 (June 2026). Download the full edition free — and subscribe to receive each monthly edition by email.

This article is provided for professional development purposes and does not constitute legal advice.