A federal judge on Thursday ordered a new trial for an 80-year-old man who filed a civil rights lawsuit against the city of Chicago contending he was beaten and forced to confess to a rape in 1951.

In his order, U.S. District Judge Ruben Castillo called the conduct of attorneys who represented the city in the 2011 federal civil trial "unethical."

"There must be a bright line between aggressive advocacy and 'win-at-all costs' unethical conduct," Castillo wrote. "The bright line has been crossed."

In his 2004 lawsuit, Oscar Walden Jr. sought $15 million from his 1951 conviction for the rape of a white woman. Walden, who is African-American, was pardoned by Gov. George Ryan in 2002.

Walden, now a minister, testified at trial that he was threatened and beaten by Chicago police into confessing. A jury rejected Walden's claims, finding in the city's favor after a six-day trial.

In their argument for a new trial, Walden's attorneys alleged that the city's attorneys, from Andrew Hale & Associates, made several missteps, among them giving the jury graphic details of the rape and other evidence that had been barred from the trial.

Castillo, in his ruling, agreed that the misconduct had a cumulatively unfair effect.

"We are elated but not surprised," said Flint Taylor, Walden's attorney. "We lived through the egregious misconduct."

Neither the attorneys nor city officials were immediately available for comment.

asweeney@tribune.com