When the legal research companies vLex and Fastcase announced their merger in April, they promised the deal would fuel new opportunities for the development of generative AI for legal research. By creating the world’s largest global legal research library, spanning more than 1 billion documents from more than 110 countries, they said, they would have the legal industry’s ultimate large language model.

“This is the biggest legal data corpus ever assembled, including highly valuable structured data with industry-standard tags and analytics,” Fastcase cofounder Ed Walters said at the time. “The combined library is the crown jewel of LLMs and the ultimate training data set for legal AI.”

Today, vLex is beginning to deliver on that promise, unveiling the beta version of a generative AI legal research platform, built on an upgraded version of vLex’s Vincent AI, an AI legal research assistant that vLex originally launched in 2018, that extends the power of generative AI across jurisdictions and languages.

vLex says that the new Vincent AI is a significant step forward for AI-powered legal analysis because it is based on one of the world’s largest online law libraries of cases, statutes, regulations, dockets, pleadings and motions, as well as secondary materials and expert treatises.

With today’s beta launch, Vincent AI works for legal research in the United Kingdom, the United States, Ireland, and Spain, in both English and Spanish. vLex will continue to add more jurisdictions and languages on a rolling basis.

Four New Skills

Yesterday, I was given a preview of Vincent AI by Walters, who is now chief strategy officer at vLex, and Damien Riehl, vice president, solutions champion, at vLex.


Vincent AI is launching with four ways of conducting research (or “skills” in AI parlance):

  • Answer a Question. Ask a question and Vincent AI will answer it with a research memo, including direct citations and links to verified sources.
  • Build an Argument. State an argument and Vincent will research and create a memorandum in support of or against that argument, complete with links to citations and sources. You can also use this to shadow box, Riehl said, by anticipating your opponent’s arguments and preparing your response to them.
  • Compare Jurisdictions. With Vincent AI, you can now compare the laws of multiple jurisdictions, including all 50 states as well as foreign language jurisdictions. If, for example, you want to compare U.K., U.S. and Spanish law, it will translate your query to search Spanish materials and translate those materials back to English to present the results. You can do a full 50-state survey in just minutes — or, eventually, a 50-country survey. Even better, this can be set to be self-updating — if a new case comes out or a new law is enacted, the survey will update and alert you.
  • Analyze Documents. This is an AI-enhanced version of Vincent’s brief analysis, allowing a user to upload a brief and get a breakdown of the related legal authorities it includes or should include.

When you ask a question in Vincent, it gives a fairly detailed response in the form of a memorandum, which starts with a quick, one-paragraph summary followed by more-detailed discussion of the applicable cases, legislation and other sources. Each memo even includes a section discussing implications and legal caveats — unlike some AI tools that only aim to please.

All the while, in the right panel of the screen, it shows links to the actual authorities. For each linked resource, it shows a summary of the case or other document, and a one-paragraph excerpt that most directly relates to your question. In addition, it provides a percentage ranking of how well the resource answered the question. Vincent only shows resources that rank above 70%.

At any point, the user can choose to eliminate any authority from the right pane simply by unchecking a box and Vincent will rerun its analysis without that authority. In a planned future update, users will be able to add their own authorities into the mix, if they know of a particular on-point authority that Vincent did not include.

Trust But Verify

In this way, Vincent is providing the user with the transparency to directly check the authorities it relied on and be assured that it did not hallucinate any of the resources. “The name of the game is trust but verify,” Riehl said. “We’re the only ones in the industry that make trust but verify super easy.”

Moreover, because Vincent is using retrieval augmented generation (RAG) to base its analysis solely on resources within the vLex database it is virtually incapable of hallucinating. When a user asks a question, Vincent converts it to a vector search to search the vLex database, and then it bases its generative AI analysis only on the resources retrieved from that search.

“It is converting that into a kind of a natural language search and searching over the jurisdiction that we asked and then coming up with results,” Walters said. “The answers can only come from this list of results, which solves the hallucination problem.”

This also addresses the “black box” issue with certain generative AI products, where it is impossible to know how the AI arrived at a certain answer, Walters said. “I like to think of ours as ‘glass box’ AI because you get to look in and have some control over it.”

In addition to these four legal research skills, Vincent AI already includes other AI-driven features. Among them, it can:

  • Spot legal issues by reading and summarizing the issues in a case.
  • Create headnote summaries for a case on the fly.
  • Find related authorities from vLex, including primary and secondary materials.

On top of all that, this release of Vincent includes Cert, the citator that Fastcase has been developing since its acquisition in 2020 of Judicata, which developed the original version of Cert. Now in Vincent AI, cases will be marked with negative-treatment tags such as “distinguished” or “overruled.” However, Cert is only active for certain states so far, with others still to be added.

Although the Vincent AI tools are currently available only to select users and only in vLex, a new version of the Fastcase platform will be rolled out next year and will include Vincent AI.

Vincent is being released today in beta to select law firms. Other law firms wishing to join the beta can request to be added to the waitlist at: www.vlex.com/insights.

Bottom Line

In a press release announcing the new Vincent AI, vLex CEO Lluís Faus said that it is a major improvement over other legal LLMs on the market. “It is as big as the jump from ChatGPT to GPT-4. The results are astonishing.”

I have not had the opportunity to be hands-on with Vincent AI, but I have now had two separate demonstrations of it, and both times, it was impressive for its ability to coalesce the law in response to a query and to formulate arguments on points of law. The memos it generated appeared to be almost ready to use as is — although it is always advisable for a lawyer to review anything AI generates before passing it on.

Two of the biggest concerns about AI in legal are hallucinations and lack of transparency into the black box. Vincent AI addresses both of those concerns by drawing its answers only from vLex data and showing the user the exact resources it is relying on and its level of confidence in their relevance.

While Vincent so far works only for research in the U.K., U.S., Ireland and Spain, the promise of a multi-lingual AI research platform is intriguing. To be able to compare the laws of multiple countries, regardless of the languages in which those laws are written, could be powerful for legal professionals with cross-border practices.

I was particularly impressed with Vincent’s ability to generate arguments for or against a proposition. I imagined myself on a call with a client or an opposing counsel, having to come up in the spur of the moment with plausible arguments on something being discussed, and turning to Vincent for a quick assist. (I should note that the argument generator currently takes as long as five minutes, but Walters said that will get faster.)

So the bottom line for me is that Vincent appears to be as close as I have seen in delivering on the promise of generative AI for legal research. I say that with the proviso that I have not recently tested what may be its two main competitors, Casetext CoCounsel and Harvey, but neither of those have all four of Vincent’s skills or the ability to answer questions across multiple nations and languages.

Photo of Bob Ambrogi Bob Ambrogi

Bob is a lawyer, veteran legal journalist, and award-winning blogger and podcaster. In 2011, he was named to the inaugural Fastcase 50, honoring “the law’s smartest, most courageous innovators, techies, visionaries and leaders.” Earlier in his career, he was editor-in-chief of several legal publications, including The National Law Journal, and editorial director of ALM’s Litigation Services Division.