Lawyers for a wrongfully convicted man who spent 21 years behind bars for a murder he didn’t commit are asking a federal judge to force former Mayor Richard M. Daley to testify in a lawsuit against the City of Chicago and disgraced Chicago Police Cmdr. Jon Burge.

Ronald Kitchen — released from prison in 2009 after his conviction was overturned — wants Daley to testify about what he knew and when about alleged torturing of African-American suspects under Burge. Daley was Cook County state’s attorney when prosecutors pushed for the death penalty against Kitchen.

Two other men who were wrongfully convicted based on confessions they say were extracted by torturers working for Burge have attempted to get Daley to talk on oath about Burge. Both times their suits were settled before Daley could be deposed.

In court papers filed Thursday, Kitchen’s attorneys say they’ve promised not to ask Daley about the recent indictment of his nephew, R.J. Vanecko. They want to focus on how he dealt with Burge, they say.

But after months of fruitless negotiation with city attorneys, they have “reached an impasse,” they write, urging Judge John Tharp to order Daley to testify.

“Mr. Daley and his City lawyers have consistently resisted voluntarily producing Mr. Daley concerning the matters alleged in this case and in the cases filed on behalf of other wrongfully convicted victims of Burge and his men,” their filing states. “He should not be permitted to indefinitely evade questioning regarding these matters simply because he was once — but is no more — the Mayor of Chicago.”

It’s now a year and a half since another judge, Elaine Bucklo, pointedly asked why the city hadn’t settled the suit, given Kitchen’s exoneration and Burge’s incarceration. Burge was convicted in June 2010 of perjury and obstruction of justice for lying in a civil court case when asked if he knew of the alleged torture that went on under his watch. He is serving a 4 1/2-year sentence in federal prison .