DENVER (CBS4)– A key witness in a death penalty case in Denver has refused to testify.

Dexter Lewis is on trial for stabbing five people to death in a Denver bar during a botched robbery attempt.

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Dexter Lewis in court on Monday (credit: CBS)

Dexter Lewis in court on Monday (credit: CBS)

Lewis, 25, is charged with killing five people inside Fero’s Bar & Grill on South Colorado Boulevard in October 2012 and then setting the building on fire.

Two co-defendants, brothers Lynell and Joseph Hill, pleaded guilty to the killings in July 2013 in an agreement to testify against Lewis. They said he had accompanied Lewis to rob the bar.

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Fero's Bar and Grill after the stabbings (credit: CBS)

Fero’s Bar and Grill after the stabbings (credit: CBS)

Joseph Hill was scheduled to testify on Thursday but refused to take the stand. He has already been sentenced to life in prison. His brother, Lynell, remains in prison on a 70-year sentence for the murders.

The victims included 53-year-old Young Suk Fero, an Aurora woman who owned the bar; Daria M. Pohl, 21, of Denver; Kellene Fallon, 44, of Denver; Ross Richter, 29, of Overland Park, Kansas; and Tereasa Beesley, 45, of Denver.

(credit: CBS)

(credit: CBS)

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Lewis also is charged with trying to hire a former prison cellmate to kill several witnesses who were expected to testify against him.