This guide, 'What Is a Reasonable Electronic Search?', is prepared by Computer Forensics Lab e-Discovery Team for UK lawyers, in-house counsel, and investigators.
Guide · 24 pages · 30 min read · Published 2026-08-29
This guide, 'What Is a Reasonable Electronic Search?', is prepared by Computer Forensics Lab e-Discovery Team for UK lawyers, in-house counsel, and investigators. It addresses the legal standard for electronic searches, referencing CPR 31.7, PD 31B, and PD 57AD. The guide covers key levers for defining a reasonable search, including Custodians, Date ranges, Sources, Keywords, Analytics and technology-assisted review (TAR), Proportionality, and Sampling and validation. It also provides insights into defensibility, negotiating search terms, common mistakes, and technical limitations. Practical sections include worked examples of overly narrow and excessively broad searches, a checklist, red flags, and suggested wording for instructions. This resource is vital for practitioners navigating the complexities of electronic discovery in the UK.
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24 pages · 30 min read
This guide, 'What Is a Reasonable Electronic Search?', is prepared by Computer Forensics Lab e-Discovery Team for UK lawyers, in-house counsel, and investigators.
Published by Computer Forensics Lab on 2026-08-29. Original material of the practice, free to read, cite and download. The authority behind this subject is Practice Direction 57AD, Disclosure in the Business and Property Courts, which you should read alongside this guide. See every guide's author and source.
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THEREASONABLESEARCH · A GUIDE FOR UK LAWYERS What Is a Reasonable Electronic Search? Custodians, Dates, Keywords, Analytics and Defensibility COMPUTER FORENSICS LAB DISCOVERY. UK
§ ABOUT THE AUTHOR PREPARED BY COMPUTER FORENSICS LAB E-DISCOVERY TEAM ACPO / NPCC DIGITAL EVIDENCE PRINCIPLES SEARCH-TERM NEGOTIATION SUPPORT TAR / CAL WITH STATISTICAL VALIDATION FULL CHAIN-OF-CUSTODY DOCUMENTATION
§ CONTENTS In this guide 01 Executive summary 02 The problem in plain English: two ways to fail 03 The legal standard: CPR 31.7, PD 31B and PD 57AD 04 Lever 1 · Custodians 05 Lever 2 · Date ranges 06 Lever 3 · Sources 07 Lever 4 · Keywords 08 Lever 5 · Analytics and technology-assisted review 09 Lever 6 · Proportionality 10 Lever 7 · Sampling and validation 11 Worked examples: the overly narrow search 12 Worked examples: the excessively broad search 13 Defensibility: the paper trail behind the search 14 Negotiating search terms with the other side 15 Common mistakes and technical limitations 16 Questions to ask · Suggested wording for instructions 17 Checklist and red flags · When to involve a digital forensic expert 18 Frequently asked questions 19 Glossary · References · Disclaimer · How a specialist laboratory can assist
§ 01 · ORIENTATION Executive summary THE HEADLINE ANSWER: WHATISAREASONABLESEARCH?
§ 02 · FIRST PRINCIPLES The problem in plain English: two ways to fail THE KEYHOLE (OVERLY NARROW) THE LANDSLIDE (EXCESSIVELY BROAD)
§ 03 · THELAW The legal standard: CPR 31.7, PD 31B and PD 57AD FOR THE PRACTITIONER
§ 04 · LEVER1 Custodians
§ 05 · LEVER2 Date ranges
§ 06 · LEVER3 Sources
§ 07 · LEVER4 Keywords
§ 08 · LEVER5 Analytics and technology-assisted review
§ 09 · LEVER6 Proportionality
§ 10 · LEVER7 Sampling and validation
§ 11 · IN THE WILD Worked examples: the overly narrow search EXAMPLE1 · THEPLEADINGSVOCABULARYTRAP EXAMPLE2 · THERANGETHATSTARTEDATTHECONTRACT EXAMPLE3 · THEMISSINGCHANNEL
§ 12 · IN THE WILD Worked examples: the excessively broad search EXAMPLE1 · THESINGLE - WORDTERMLIST EXAMPLE2 · RESTOREEVERYTHING, JUST IN CASE EXAMPLE3 · EVERY ON E, TOBESAFE
§ 13 · THEPAPERTRAIL Defensibility: the paper trail behind the search DOCUMENT WHAT IT RECORDS
§ 14 · ACROSS THE TABLE Negotiating search terms with the other side
§ 15 · WHEREITGOESWRONG Common mistakes and technical limitations Common mistakes Technical limitations
§ 16 · INTERROGATORIES & DRAFTING AIDS Questions to ask · Suggested wording for instructions Ask your client Ask your opponent Ask an e Discovery provider SUGGESTED WORDING · SEARCHPROTOCOLPREAMBLE ( CORE PA R AG RAPHS ) SUGGESTED WORDING · PROPOSINGTERMSTOTHEOTHERSIDE
§ 17 · QUICK CONTROL Checklist and red flags · When to involve a digital forensic expert The reasonable-search checklist Red flags When to involve a digital forensic expert
§ 18 · COMMON QUESTIONS Frequently asked questions What is a reasonable electronic search? Do we have to search backups? Can we rely on keywords alone? Are we required to use TAR? A relevant document has surfaced that our search never caught. Is the certificate wrong? Who decides if the parties cannot agree terms?
§ 19 · REFERENCE Glossary TAR Sources and authoritative references DISCLAIMER
§ HOW A SPECIALIST LABORATORY CAN ASSIST Working with Computer Forensics Lab Speak to a forensic examiner, not a salesperson. INSTRUCTTHELAB NEWENQUIRIESEMAILE - DISCOVERY
17 pages · 21 min read
This guide, 'How To Design Defensible Keyword Searches', is for UK lawyers, in-house counsel and investigators.
17 pages · 22 min read
This guide, 'Technology-Assisted Review for UK Lawyers', covers Predictive Coding, Continuous Active Learning, and defending the machine's judgement.
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