Texas man convicted of killing six family members of his ex-wife, including four children

A Houston jury convicted a man for murdering six members of his ex-wife's family on Thursday, thereby rejecting his defense of insanity.

Ronald Lee Haskell's lawyers said he heard voices telling him to kill members of the Stay family in 2014. According to the prosecutor, Haskell, 39, had planned to kill anyone who helped his ex-wife, Melannie Lyon after leaving him.

Authorities say Haskell came from California and harassed the Lyon family for two days before committing the killings.

The victims include Stephen Stay, 39, and his wife Katie, 34, and their children, Zach, 4, Rebecca, 7, Emily, 9, and Bryan. Katie Stay was the sister of Mélanie Lyon.

Cassidy Stay, who was 15 at the time of the shooting, survived playing death after being shot in the head. She testified that Haskell forced everyone in the Houston home to lie face down in the living room before shooting at them. He later tried to visit the parents and brother of his ex-wife, but was arrested by the police.

A forensic psychiatrist who testified for the defense stated that Haskell was suffering from a serious mental illness that prevented him from knowing what was right. The psychiatrist said that Haskell was suffering from a form of bipolar disorder, a brain disorder resulting in unusual mood changes, as well as a schizoaffective disorder, characterized by hallucinations or delusions.

Ronald Haskell is appearing for his trial in Houston last month. (Steve Gonzales / Houston Chronicle via AP, File)

In Texas, a defense against madness is rarely used and rarely succeeds.

Lyon testified that Haskell physically assaulted him, along with their children. She eventually took them away and moved from Utah to Texas to be with her family after the couple's divorce.

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Prosecutors said Haskell had simulated the symptoms of mental illness and carefully planned the killings, disguising himself as a FedEx delivery driver to enter the Stay family home.

"We are grateful to the jurors for paying close attention to each and every piece of evidence presented in recent weeks," said Harris County Attorney Kim Ogg in a statement. "There has never been a reasonable doubt that Haskell planned and meticulously executed the Stay family massacre."

The jurors deliberated for eight hours over two days before taking a decision. The penalty phase of the trial must begin Monday. Prosecutors demand the death penalty.

Associated Press contributed to this report.