Last month, during the guilt phase of the trial, Christensen's father was his only family member who was in court every day. Wednesday when he took the stand, it unleashed a flood of emotion.
Brendt Christensen, typically stoic, teared up in court as Michael Christensen said he still loves his son. The father was asked if he had a message for Zhang's family.
"I'm sorry my son was the cause of your pain," Michael said through tears.
But Zhang's relatives weren't in the courtroom to hear it; they had left minutes earlier.
During his testimony, Michael Christensen recounted his son's chaotic childhood, including recurring bouts of night terrors and waking nightmares that continued into adulthood, a bizarre suicide attempt at the age of 15, and his mother battle with alcoholism and depression which were not unlike Brendt's own struggles.
The defense argued these "mitigating factors," including addiction and mental illness, should spare Christensen the death penalty.
In stark contrast, the prosecution painted the murder of Zhang as "cold, calculated, cruel and months in the making."
Tuesday Zhang's father and brother testified in court. The jury was also shown a video of her mother being interviewed by prosecutors in court following the guilty verdict, in which Lifeng Ye spoke tearfully.
"My daughter did not get to wear a wedding dress," she said. "I really wanted to be a grandma."
At that point in the video, a female juror left the courtroom in tears, apparently overwhelmed, and the judge called a brief recess. That prompted Christensen's defense Wednesday morning to request a mistrial, or at least the removal of the juror, but the motion was denied.
In addition to Christensen's father, the jury heard from two of his uncles, one on each side of his family. Both testified that several family members, across generations, had battled addiction and mental illness.
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