HOUSTON  Lawyers for a Texas inmate facing execution next week filed court papers on Thursday accusing the judge at his double-murder trial of having an affair with the prosecutor.

The papers, filed in the Texas Court of Criminal Appeals, argue that the relationship between the judge, Verla Sue Holland, and the man who was district attorney of Collin County, Tom O’Connell, should nullify the conviction of the inmate, Charles Hood, in 1990.

The filing says that Judge Holland had a “personal and direct interest in the outcome of the case” and that “the wall of silence that has long protected Judge Holland must now come down.”

“Under these circumstances,” Gregory Wiercioch, Mr. Hood’s lead lawyer, said in an interview, “Judge Holland had a clear duty to let the parties know about her relationship and to recuse herself, because anybody knowing these facts would be shocked that she presided over this capital murder trial.”