'Voices in his head': Police reveal tragic buildup to Concord teen allegedly killing his mother

Feb. 17--CONCORD -- A Concord man who allegedly admitted to fatally stabbing his mother in the entryway of her apartment told investigators he was hearing "voices in his head" ordering the killing, police said.

Police would later learn that Harrison Mercier, 18, had been struggling with mental illness for months before he allegedly stabbed 59-year-old Elizabeth Barry in her apartment on the 3500 block of Treat Boulevard. Police say Mercier called 9-1-1 on himself after the killing, telling investigators he was responding to voice commands in his head.

Mercier also allegedly told investigators that he had made videos about the Feb. 5 killing. Police are investigating the claim. He also suggested the voices in his head may have come from horror movies he had been watching, referencing the "Saw" series by name, police said.

Mercier's account of the killing could play heavily into his legal defense. Contra Costa prosecutors charged him with murder and use a knife, and he faces a life sentence. By contrast, if he pleads not guilty by reason of insanity, and is acquitted, he fill face time in a mental institution.

According to police, family members noticed Mercier had been struggling with mental illness for at least a year. His parents, divorced and living apart, had made efforts to help him. Just days before Barry's death, Mercier had been admitted to a 30-day Outward Bound hiking program, and had dropped out within a week.

After dropping out, Mercier went to his father's home in Oakland. Upon Mercier's return, his father decided Mercier could benefit from time with his mother, and suggested he visit her. Mercier took a bus to Concord to visit his mother on Feb. 2, three days before the killing.

If Mercier enters an insanity plea, it would require two trials. In the first, jurors would determine whether he was factually guilty of murder. Upon a conviction, the same jury would then review evidence to determine whether he was legally sane at the time of the killing.

Such a move is rare, though two recent examples have had wildly different results. Last September, a Walnut Creek security guard reached a plea deal with prosecutors where he was sentenced to 15 years to life in a mental institution, for killing a colleague for no apparent reason. He blamed voices in his head and had recently run out of schizophrenia medication.

In 2017, William Shultz received a life sentence for murdering 9-year-old Jordan Almgren during a sleepover at Almgren's home. Shultz, 18 at the time, said he believed the world was ending and wanted to see what it was like to kill someone. He was convicted of first degree murder, found legally sane, and sentenced to life without a chance for parole for 30 years.

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