Mark Hacking pleaded not guilty Friday to first-degree murder in the death of his wife, whose remains were found in a landfill more than two months after her disappearance.

The innocent plea infuriated Lori Hacking's family — her brother had urged Hacking to "be a man" and accept punishment, and her mother said she felt outrage for Lori and her unborn child.

"I know that one day Mark will receive perfect judgment from the only judge who knows every detail of what he did that terrible night," the mother, Thelma Soares, told reporters outside a courtroom where Hacking appeared shackled and wearing a bulletproof vest. He was surrounded by a dozen bailiffs.

Judge Denise Lindberg set Hacking's trial for April 18. Deputy District Attorney Robert Stott said he was not seeking the death penalty because he can't prove she was five weeks pregnant, as she told friends. An autopsy of her decomposed remains couldn't determine how she died.

Authorities believe Lori Hacking, 27, was killed July 19 after learning her husband wasn't enrolled in medical school in North Carolina, though they were packing to move there. It was among a series of deceptions Mark Hacking had perpetuated over several years, police say.

Hacking's defense attorney has indicated he would take the case to trial and challenge Hacking's alleged confession to his brothers that he shot his wife in the head while she slept and disposed of her remains, the weapon and a mattress in separate trash bins.

"Any time they call a family member to testify against another family member, it's going to be painful," said Scott Hacking, a physician who said his brother was "under extensive psychiatric testing" while in jail.

Defense attorney Gil Athay declined to discuss his plans Friday, saying, "We don't talk about those things." Stott said no discussions have been held on a plea agreement.

Hacking's parents, Douglas and Janet Hacking, also attended the hearing Friday, but left the courtroom without comment.

Hacking's plea came after the victim's brother, Paul Soares, appealed to Hacking to "take responsibility for your actions" and plead guilty to her murder.

"Save your family the grief and cost of this attorney. Just plead guilty for once. Just tell the truth," he wrote in a 2 1/2-page letter to Hacking at jail. A copy was obtained by The Associated Press and first reported Friday in the Deseret Morning News.

"Lori was sleeping like a princess in bed and you took her life ... if that is even how it happened. Are you being honest in that? Have you ever told the truth?"

Her father, Eraldo Soares, said Hacking's innocent plea was prolonging the family's pain.

"I'm not here to judge Mark. I have to leave that to be decided in court. I'm not going to be angry. I have to accept what is going on," he said.

Scott Hacking said he understood his brother was writing a book in jail "to get out the entire truth," but that his family no longer was asking for details about Lori Hacking's death.