Bergdahl faces up to life in prison after he pleaded guilty to desertion and misbehavior before the enemy for walking off his Army base in Afghanistan in June 2009. He was subsequently captured by the Taliban and held for five years before he was freed in a prisoner exchange between the militant group and the Obama administration in May 2014.
Before answering any questions, he read a statement in open court, admitting that what he did was wrong and that he understands the pain and suffering that he caused so many people, including his platoon mates.
"Saying I'm sorry isn't enough. My words can't take away the pain that people have been through," the 31-year old said. "I was trying to help, and the fact that I did not breaks my heart."
Bergdahl claims that he left his base to report misconduct in his unit to an officer.
During two hours of questioning from his lawyers, Bergdahl talked about the physical abuse, including living in a metal cage for much of the time, being beaten and burned by his captors, and being chained spread-eagle to a bed. He was so weak at times that he couldn’t even stand up and didn’t know who he was or where he was, he said.
His lawyers showed several items, including handcuffs, leg shackle chains and padlocks, that they said were similar to the ones used on him in captivity, with Bergdahl describing the open sores on his ankles and hands from the tightness of the chains and shackles. He also said the Taliban would at times put some sort of chemical or hallucinogen in his cell that made him disoriented and sick, calling it "terrifying."
But "the worst," he said, "was the constant deterioration of everything. The constant pain of my body falling apart. The constant internal screams from my mind ... I could see my ribs, my joints. There was nothing left."
That trauma has not subsided either, he said. Back in the U.S. for three-and-a-half years now, he still hardly sleeps, he said, because he has nightmares and flashbacks -- often waking up and not knowing who he is or where he is. Mundane things, like the crowing of a rooster, remind him of some of the darkest details of his time in captivity, like a particularly gruesome execution video the Taliban forced him to watch -- something they constantly threatened to do to him, he said.
That video was shown in court, in a moment where the press was cleared out because it is classified.
When asked what kept him going for those five years of captivity, Bergdahl replied, "Trying to find a way to escape. Trying to gather as much intel as I could, so I could get that back out. Not letting them win."
The testimony wrapped up a key day in the sentencing phase of Bergdahl's trial, where the judge denied a motion by the defense to dismiss the case on the grounds of what's called "unlawful command influence." That's when a higher level military figure, including the president and commander-in-chief, influences or appears to influence judicial proceedings. Army Col. Jeffery Nance ruled that the court has not been directly affected and said he remains uninfluenced by Trump's remarks.
As a candidate, Trump disparaged Bergdahl and the Obama administration's agreement to get him back from the Taliban. On Oct. 16, 2015, for example, Trump called him "a rotten traitor" and suggested he should be shot or dropped from an airplane.
"In the old days he'd get shot for treason," he told a crowd of supporters. "If I win, I might just have him floating right in the middle of that place and drop him, boom. Let 'em have him. ... I mean, that's cheaper than a bullet."
More recently, Trump declined to comment on Bergdahl's case the day the soldier entered his guilty plea, but Trump told reporters, "I think people have heard my comments in the past."
Even those comments were seen by Nance as unlawful command influence, writing in his ruling, "The plain meaning of the president’s words to any reasonable hearer could be that in spite of knowing that he should not comment on the pending sentencing in this case, he wanted to make sure that everyone remembered what he really thinks should happen to the accused."
But instead of throwing the case out, Nance may lighten his sentence because of those comments.
The other mitigating factors in Bergdahl's sentencing, however, could work against him -- the emotional testimony of the soldiers who went searching for him and were injured. The prosecution had those soldiers and their family members share their stories as evidence that Bergdahl deserves a harsh punishment for putting their lives in danger.
Some of the most vivid testimony last week came from Jonathan Morita, whose hand was shattered by a rocket-propelled grenade in an ambush.
Today, Master Sgt. Mark Allen's wife Shannon Allen and his doctor Rafael S. Mascarinas III told Mark Allen's story.
Allen was on a search mission with U.S. and Afghan troops in July 2009 when the group was attacked by insurgents and Allen was shot in the head. His life was saved by the medical teams in the field, but doctors were forced to remove both frontal lobes of Allen's brain, according to Dr. Mascarinas's testimony, the region of the brain that controls speaking and movement.
"His eyes were open, but he didn’t have any awareness of his environment, nor was he responding to commands," Mascarinas said of Allen when he was admitted to his hospital in August 2009, noting Allen was in a "vegetative state" and today remains in "a minimally conscious state" and unable to speak.
Shannon Allen described her husband as a "happy-go-lucky guy," a very active father who played with his son all the time, loved to go hiking and do outdoor activities.
But she cried as she shared, "The interactions have changed significantly. ... His involvement now is much more passive, he’s not able to reach out to her or to talk to her," she said of their daughter.
"He lost me as a wife because I have become his caregiver," she added, noting that he cannot be left alone because he's prone to seizures. "We can't even hold hands anymore without me prying open his."
The defense's case will continue on Tuesday, although it's unclear if Bergdahl will continue to testify before the court. The defense expects to be done with witness testimony on Wednesday, and then after closing arguments, the case will be in the judge's hands, with a decision possibly as soon as the end of this week.