Staff Sgt. Patrick Ziegler was among the first to testify, telling jurors how he was shot four times and underwent emergency surgery that removed about 20 percent of his brain. Doctors initially expected him to die or remain in a vegetative state.
Ziegler was hospitalized for about 11 months and had 10 surgeries. He is now paralyzed on his left side, unable to use his left hand, and blind spots in both eyes prevent him from driving.
"I think I'm hopeful I'll continue to recover some movement, but eventually I'll succumb to my wounds and I won't be able to function," Ziegler said.
The married father said he has trouble caring for his 10-month-old son, "like a normal father would" and described his cognitive level as that of a 10th- or 11th-grader. He also said he has fought severe depression.
"I'm a lot angrier and lot darker than I used to be," he said, adding that the injuries had "pretty much affected every facet of my personality."
Shoua Her wiped away tears as she recalled how she and her husband, Pfc. Kham Xiong, talked about growing old together and having more children. Now, she said, their children know their slain father only through memories and stories.
"We had talked about how excited we were to purchase our first home. We talked about vacations and places we wanted to go visit. And all that was stripped away from me," she said.
"Our daughter will not have her dad to walk her down the aisle. My two sons will never have their dad to take them fishing or (teach them) sports or how to be a gentleman."
"I miss him a lot," she added. "I miss his soft, gentle hands. How he holds me. He made me feel safe and secure. Now the other side of the bed is empty and cold. I feel dead but yet alive."
As she testified, one juror, a male officer, fought back tears.
Juan Velez, the father of Pvt. Francheska Velez, said his family hasn't come to grips with her death. His 21-year-old daughter was pregnant, and several witnesses testified about hearing her cry, "My baby! My baby!" during the attack.
"That man did not just kill 13, he killed 15. He killed my grandson (Velez' unborn child) and myself," he said in Spanish. "It hurt me to the bottom of my soul."
Another widow, Cristi Greene, struggled through sobs as she recalled her husband of 3½ years, Pfc. Frederick Greene.
"I can't explain how hard it's been. You open a box, looking at a picture. It hurts so bad. It's all you're ever going to have," she said.
Greene's mother, Karen Nourse, said everything changed the day Army officers arrived at her daughter-in-law's home for the death notification: "I get up in the morning and I prepare myself to get through a day without him. And that's difficult. And it won't ever go away. Ever," she said.
The hearing ended for the day after a dozen people testified. Hasan asked for three recesses through the day, and the judge granted two of them.
Other widows, mothers, children and siblings of the slain also are expected this week to tell the jury of 13 high-ranking military officers about their loves ones and describe the pain of living without them. What they won't be allowed to talk about are their feelings toward Hasan or what punishment they think he deserves.
Hasan, an American-born Muslim, has admitted carrying out the attack and showed no reaction when he was found guilty. He is representing himself during his trial, yet he called no witnesses, declined to testify and questioned only three of prosecutors' nearly 90 witnesses before he was convicted.
Earlier Monday, the judge asked Hasan if he wanted to continue representing himself and advised against it, as she has repeatedly done during the trial.
"You understand that this is the stage of trial ... you are staking your life on decisions you make. You understand?" the judge, Col. Tara Osborn, asked.
"I do," Hasan said.
At the minimum, the 42-year-old Hasan will spend the rest of his life in prison.
No American soldier has been executed since 1961. Many military death row inmates have had their sentences overturned on appeal, which are automatic when jurors unanimously vote for the death penalty. The U.S. president must eventually approve a military death sentence.