A Maryland man who stabbed his girlfriend to death after he envisioned her as “the devil” or “a Dracula” failed to win his attempt to avoid prison after a jury on Wednesday rejected his insanity defense.

Barry Kin Lui had already pleaded guilty to second-degree murder in the 2011 killing of Lan Mu Do, but believed he should not be held “criminally responsible,” seeking Maryland’s version of what is commonly referred to as an insanity defense. A Prince George’s County jury, however, returned a verdict saying Lui was criminally responsible for Do’s slaying. If the jury had returned a verdict in Lui’s favor, he could have served his sentence in a state mental institution instead of prison.

For a week, the jury heard testimony from psychologists, Lui and other witnesses to decide whether Lui suffered from a mental disorder that drove him to slay Do.

During the trial, Lui testified that Do blackmailed him into signing over the deed to his Gaithersburg house less than a year into their relationship. He said when she didn’t return the Gaithersburg property and threatened to kick him out of the Beltsville house where they were living together at the time, the couple got into an argument, and he stabbed her.

Lui’s sentencing is set for July 2. State prosecutors are expected to ask for a 30-year sentence for Lui, officials from the Prince George’s County State’s Attorney’s Office said.

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