Lawyers do not have to be expert mathematicians; they do not even have to know calculus. However, all lawyers should have a solid understanding of complex math, accounting and algebra to fulfill their job requirements. Furthermore, scoring well on the LSAT entrance exam requires some math understanding.
Almost every lawyer needs some amount of math to conduct their jobs properly. Even criminal defendants need to calculate jail time and laying out a case for acquittal. Lawyers also need to structure their arguments much like a mathematician structures a proof. They start out with all the facts, then state the laws and precedents and finally use all of that information to deduce that the accused is guilty or innocent.
Lawyers often run their own offices, or at the very minimum must have input and understanding of the way their firms are run. They need math to understand income and liabilities, cash flow and expenses. In addition, lawyers must have a good math sense to leave cash on hand for future outlays. Partners in large firms are given "equity" in the firm, which entitles them to a percentage of the firm's overall profits. Lawyers with equity must calculate their income based on the firm's income.
Taxes, Patent, Securities and Other Specialties
Tax professionals use math on a daily basis to provide advice for clients and to create all of the scenarios that could possibly reduce a client's tax burden. Patent lawyers also use math as part of their cases to scientifically prove or disprove a patent liability. Securities lawyers calculate equity, debt and capital structure in disclosure documents. In fact, a variety of specialists must use math in their daily work.
The LSAT, which is the entrance exam for all law schools in the U.S., has two key sections which require math comprehension. These are the logical reasoning section and the analytical reasoning section. Both sections require deductive analysis similar to that used in math proofs. They also require some simple arithmetic to solve their puzzles. In both sections, a strong math or science background is an advantage to the test taker.