SAN FRANCISCO — Silicon Valley is usually measured on its products and profits. Now, in a rare turnabout, it is about to be judged on its behavior.

The venerable venture firm Kleiner Perkins Caufield & Byers, which nurtured such famous Internet start-ups as Google and Amazon, has been on trial here for the last month. Ellen Pao, a former junior partner at Kleiner, says it discriminated against her, retaliated when she complained and ultimately fired her.

In closing arguments that began Tuesday before a packed courtroom, the top-flight litigators trying the case had one last opportunity to sway the jury. The ethnically diverse collection of men and women who will render a verdict — a subway station manager, a painter, a prison nurse — watched intently but gave nothing away, the way they have watched the whole trial.

“We are all here today because Kleiner Perkins broke the law,” said Alan B. Exelrod, Ms. Pao’s attorney. “Men were judged by one standard and women by another.”