CHICAGO — The artist Peter Doig took the stand here Monday in an odd federal court case in which the owner of a landscape painting is accusing Mr. Doig of falsely denying that he created the work while a young man in Canada.

In a brief opening statement, William F. Zieske, a lawyer for the owner, said the evidence would prove that a painting bought in 1976 by his client, a former correction officer named Robert Fletcher, and signed “Pete Doige,” is “indeed the work of Peter Doig.”

The painting was carried into the courtroom in a cardboard box and unceremoniously placed on a metal easel a few feet from the artist and his team of lawyers. “This is not a work painted by someone with no artistry or no artistic talent,” Mr. Zieske said. “It is a work of master artistic talent.”

But Matthew S. Dontzin, a lawyer for the artist, a popular painter whose works routinely fetch $10 million, argued that his client has been suffering through a nightmare of “bullying tactics” and money demands from plaintiffs who “have not produced any documents or one witness to show that Doig painted this or Doig didn’t.”