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CCTV & DVREVIDENCE · A GUIDE FOR UK LAWYERS Recovering Deleted CCTV and DVR Footage The Overwrite Clock, the Proprietary Recorder and the Race to Preserve the Frame COMPUTER FORENSICS LAB

§ ABOUT THE AUTHOR PREPARED BY COMPUTER FORENSICS LAB E-DISCOVERY TEAM PROPRIETARY-FORMAT DECODING CPR PART 35 EXPERT REPORT S FULL CHAIN-OF-CUSTODY DOCUMENTATION

§ CONTENTS In this guide 01 Executive summary 02 The problem in plain English: footage that overwrites itself 03 How DVR and CCTV systems store and overwrite footage 04 Preserving before the loop: the urgent first steps 05 Recovering deleted and overwritten footage 06 Formats, timestamps and authenticity 07 Deployment: disclosure, the lost frame and the filmed monitor 08 Source architecture: where else the evidence lives 09 Worked examples 10 Common mistakes and technical limitations 11 Questions to ask · Suggested wording 12 Checklist and red flags · When to involve a digital forensic expert 13 Frequently asked questions 14 Glossary · References · Disclaimer · How a specialist laboratory can assist

§ 01 · ORIENTATION Executive summary weeks: preservation is the emergency, it comes before analysis, and the single most important act is to secure the recording, or the whole recorder, before the loop erases it.

§ 02 · FIRST PRINCIPLES The problem in plain English: footage that overwrites itself

§ 03 · HOWITSTORESFOOTAGE How DVR and CCTV systems store and overwrite footage CAMERAS RECORDER RING BUFFER OVERWRITE PRESERVE FIRST