James Holmes’ father says he didn’t know son was mentally ill

The father of convicted “Dark Knight” murderer James Holmes ended a three-year public silence on Tuesday, taking the stand at his son’s sentencing to make a final plea to save him from execution.

Robert Holmes said he and his wife had no idea before the July 2012 theater massacre that their eldest child was mentally ill, or harbored impulses to kill.

The father, a retired financial fraud analyst who admitted to having trouble expressing his own emotions, also said he still loved his son.

Asked by a defense lawyer why, Robert Holmes responded, “Well, he’s my son and, you know, we always got along pretty well and he was actually an excellent kid.”

RELATED: Jury finds Aurora shooter James Holmes guilty of first degree murder

His testimony, which was to be followed by that of his wife, Arlene, marked the first time either of them have spoken publicly since the shooting, in which their son opened fire in a crowded midnight screening of “The Dark Knight Rises” in Aurora, Colorado, killing 12 people and injuring 70.

Their sole public statement had been a letter they penned to prosecutors asking for his life to be spared.

For the three months James Holmes has been on trial, Robert and Arlene Holmes have sat quietly behind him.

Their testimony is expected to cap the defense team’s effort to persuade the jury to sentence Holmes to life in prison.

The same jury convicted Holmes of the massacre this month, rejecting defense lawyers’ arguments that he was legally insane at the time of the attack. Two state psychiatrists and two defense psychiatrists agreed Holmes suffers from mental illness. But the state doctors also testified that he could distinguish right from wrong, the legal criteria in Colorado to prove sanity.

This article originally appeared on NBCNews.com.

James Holmes' father says he didn't know son was mentally ill