WICHITA, Kan. — A Kansas courtroom with an octogenarian in the defendant’s chair will be the unlikely scene for a retelling of the horrors of the 1994 genocide in Rwanda.

Jury selection began on Tuesday in the trial of Lazare Kobagaya, 84, a native of Rwanda who is charged with illegally obtaining United States citizenship and misusing an alien registration card. Prosecutors say Mr. Kobagaya lied on his citizenship application when he denied participating in genocide, and they are bringing witnesses from Africa to try to prove it.

“The evidence will involve some pretty dramatic, grim, terrible evidence, I think,” Judge Monti L. Belot of Federal District Court told potential jurors.

“It’s my understanding that there will be people here who actually committed genocide,” he added.

Lawyers for Mr. Kobagaya have said their client’s name never surfaced in impartial investigations of the violence in his native land. It was only when he made a statement on behalf of another Rwandan who had been charged with genocide by Finnish courts that he became a target of United States investigators, the lawyers say....