Missoula, Montana (CNN) -- The defense and prosecution agree on this much: Jordan Linn Graham pushed her husband of eight days, and he fell off a cliff to his death in Glacier National Park in Montana. The question for jurors will be whether Graham's act was murder or a case of self-defense that ended tragically. The two sides set out their opening arguments Monday about what took place as Graham's trial began in U.S. District Court in Missoula, Montana. Prosecutors said they would show that Graham, 21, was having serious second thoughts about her marriage before her husband's death and willfully lied to police after it.
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NEW: Prosecutors say Jordan Linn Graham was unhappy before her husband's death
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NEW: The defense says his death was the result of an "argument-grab-push-fall"
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NEW: The court hears text messages that Graham sent around the time of the death
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Graham has admitted pushing Cody Johnson during an argument in a national park
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