Large productions are reviewed with the assistance of software, and courts have accepted the methods where the process is documented.
Search terms. Negotiated, tested against a sample, and refined by measuring precision and recall. Terms agreed without testing routinely capture enormous volumes of irrelevant material or miss key documents.
Technology-assisted review. A model trained on coding decisions by experienced reviewers, ranking documents by likely relevance, with review proceeding until a defined recall target is reached and validated by sampling.
Validation. A statistically valid sample of the documents not produced, reviewed to estimate what was missed. This is what makes the process defensible, and it should be planned before review begins.
Transparency. Courts and opposing parties increasingly expect disclosure of the methodology, though not of the training documents themselves in most decisions.
Privilege. Software-assisted privilege identification supplemented by review of documents involving counsel, with quality control sampling, and a claw-back order in place.
Cost. The dominant expense in document-heavy litigation, and the place where proportionality arguments have the most effect.
Documentation. A written protocol recording the decisions, the testing and the validation, prepared as the work is done rather than reconstructed when challenged.