A legal AI assistant is software that answers legal questions in plain English, drafts research memos and court documents, and reviews large sets of documents for lawyers. It is built on a large language model, an AI model trained on huge amounts of text. Law firms and companies' legal teams pay for it by subscription, usually for each lawyer who uses it.
Its first tasks are the work of junior lawyers, who are called associates: research memos, first drafts of court documents, and reading hundreds of documents for one deal or case.
Take, for example, a law firm in Mumbai that represents a company buying a chain of 40 restaurants. Each restaurant runs in rented premises, so there are 40 leases. The buyer needs three answers from each lease: how long the lock-in period is, how fast the rent rises, and whether the landlord can end the lease if the chain changes owner. Reading 40 leases used to take two associates about a week. The assistant reads all 40 in under an hour. It produces a table with one row for each lease and one column for each question, and it quotes the clause behind each answer. The associates then check every row where the assistant marked a risk, and a sample of the others. The model drafts and a person approves; this way of working is called human in the loop.
The assistant can also answer a research question, such as whether a landlord may end a lease early for late rent. Here the main risk is AI hallucination: a model can invent a judgment, with a name and a citation, that does not exist. Courts have fined lawyers for citing such invented cases. So a reliable assistant does not answer from the model's memory. It first searches a legal research database for real judgments and statutes. Then the model writes the answer only from those passages, with a link to each one. This method is called retrieval-augmented generation (RAG).
The assistant also changes how firms charge. If work that took a week now takes an hour, a firm that charges by the hour earns less for it. This tension is described in billable hours.
How is it different from AI contract review? Contract review software checks a company's own contracts against that company's rules, inside its contract system. A legal AI assistant is a general tool for a lawyer's research, drafting and review.