Trisha Smith, an assistant district attorney for Hughes County, said this evidence was tested by investigators.
“They came back a match to Mr. Smith,” the prosecutor said.
A civil lawsuit, filed in federal court by Demings' attorneys, claims the DNA evidence belongs to Smith.
Smith and Corrections Corporation of America are listed as defendants in the federal case.
The inmate is claiming his civil rights were violated and he was subjected to cruel and unusual punishment when Smith forced him to perform oral sex, according to the suit.
The civil case is pending, records show, but a settlement conference has been ordered by the presiding judge.
Shortly before he was interviewed by James Parvin, an investigator for the state Corrections Department, Smith took a job as a prison guard at the Oklahoma State Penitentiary — the facility that houses death row.
Parvin was assigned the case because Demings was under the purview of the Corrections Department at the time of the incident.
Jerry Massie, spokesman for the state Corrections Department, said Smith was hired July 1, 2011, to work at the Oklahoma State Penitentiary.
Smith was “discharged” from his job July 27, 2011, Massie said, the same day he was interviewed by Parvin in connection with the sexual assault case involving Demings.