Triumph Controls UK Ltd & Anor v Primus International Holding Co & Ors

Electronic disclosure must be managed proportionately, but proportionality does not justify an unexplained or unilateral reduction of a potentially relevant document population. Parties should discuss and agree the search methodology, filtering and use of computer-assisted review at an early stage. A computer-assisted review and sampling exercise should be transparent and independently verifiable, with relevance criteria applied consistently. Where the available evidence suggests that disclosure is materially incomplete, the court may order a further, targeted manual review. The scope of that review should reflect the value and complexity of the claim, the likely benefit of further disclosure, the costs involved and the effect on the trial timetable.

The claimants brought warranty claims worth approximately US$65 million arising from the purchase of an aerospace business. The defendants applied for further disclosure concerning a large shared drive and approximately 220,000 documents identified by agreed keyword searches but not subjected to further review.

The court considered whether the claimants’ reduction of the shared-drive data was reasonable and proportionate, and whether their unilateral use of computer-assisted review and limited sampling provided an adequate basis for omitting further review. The central issue was what further disclosure, if any, was justified before trial.

1. Shared-drive folders and file paths. The claimants’ approach was reasonable and proportionate. Only two further folders or file paths had subsequently produced disclosure, the defendants could not identify particular missing locations likely to contain relevant material, and the complaint was raised approximately 17 months after the process had been disclosed. No further disclosure was ordered on this issue.
2. Unreviewed documents. The claimants’ treatment of the remaining 220,000 documents was inadequate. Their disclosure questionnaire had indicated that all documents responsive to the agreed keywords would be manually reviewed, but the later decision to stop the review and rely on a unilateral computer-assisted review process was not sufficiently explained.
3. The computer-assisted review and sampling exercise lacked transparency and independent verifiability. There was insufficient information about how the system was configured, how relevance criteria were applied, the sampling methodology, tolerances and number of sampling rounds. The involvement of numerous lawyers without an apparent overseeing senior lawyer also created a risk that the relevance criteria had not been consistently applied.
4. Consistently with the principles in Nichia Corporation v Argos Limited [2007] EWCA Civ. 741, disclosure rules embody a proportionate compromise rather than a requirement for perfect justice. The guidance in Digicel (St Lucia) Limited and Others v Cable & Wireless Plc and Others [2008] EWHC 2522 (Ch), Practice Direction 31B and the TCC e-disclosure protocol emphasised early co-operation and the risks of unilateral searches. The guidelines in Pyrrho Investments Limited and Another v MWB Property Limited and Others [2016] EWHC 256 (Ch) were also useful, although the recommendation of a single senior lawyer was regarded as guidance rather than an inflexible requirement.
5. Taking account of the modest proportion of documents disclosed, the later disclosure of approximately 2,000 documents responsive to the original keywords, the document-heavy nature of the allegations and the unreliability of the 0.38 per cent prediction, the court ordered a proportionate further exercise. The parties were required to agree a methodology for manually reviewing a 25 per cent sample of the 220,000 documents within three weeks, with the results reported in an agreed letter.