The sprawling civil fraud trial of Donald J. Trump dragged to an end on Wednesday as defense lawyers interrupted a witness who was testifying about the principles of accounting with a spirited argument over the difference between the words “could” and “would.”

The witness, Eric Lewis, a professor at Cornell University’s business school, was the last to appear at the trial, which stems from a lawsuit filed by the New York attorney general, Letitia James, accusing the former president of fraudulently inflating his net worth to obtain favorable treatment from banks and insurers.

The conclusion of Mr. Lewis’s appearance shortly after noon signified the end of the trial’s testimony, though a verdict remains weeks away.

Next month, the parties are expected to submit closing briefs, drawing on evidence to present their cases and argue before the judge on Jan. 11. The judge, Arthur F. Engoron, will then decide the outcome, a decision expected in late January at the earliest.

Ms. James, a Democrat, has asked that Justice Engoron fine Mr. Trump $250 million or more and bar him and the other defendants in the case from running a business in New York. Mr. Trump, a Republican, has said the case is part of a political vendetta against him.

Mr. Lewis’s testimony provided a fitting conclusion to a trial that was occasionally scintillating, but more often stultifying. The proceedings were dry, muddled and characterized by fighting between the parties — particularly when Mr. Trump was in attendance.