WASHINGTON, June 13  A pair of charcoal-colored pants at the center of a $54 million lawsuit was unfurled in a courtroom here on Wednesday, introduced into evidence by a defense lawyer who called the lawsuit a “nightmare” for his clients.

“It’s a story of how one man has ruthlessly abused the legal system and one statute and caused a great deal of suffering for what was essentially a hardworking mom-and-pop business,” the lawyer, Christopher Manning, said, referring to Roy L. Pearson Jr., a District of Columbia administrative law judge who is suing the owners of a neighborhood dry-cleaning shop here.

Mr. Pearson is alleging that the shop, Custom Dry Cleaners, returned the wrong pair of pants to him, and along the way broke promises made in signs saying “Same Day Service” and “Satisfaction Guaranteed.”

Judge Judith Bartnoff is hearing the case and is expected to make a ruling by the end of next week.

In emotional testimony, Soo Chung, one of the business’s owners, said the case had created an ordeal for her and her family, who sat in the front rows of the courtroom.