Patricia Harris found the body of her son, Jonathan, who was 26 when this photo of her son was taken. (Left photo by Dan Morse/The Washington Post; family photo at right)

Patricia Harris walked to the witness stand, prepared to talk about her son Jonathan’s brave life and tragic death.

“He was always, always a fighter,” Harris told the Montgomery County jury. “He was strong.”

The hour-long testimony, during which Harris described how she discovered her son’s strangled, beaten body, became the emotional center of a trial that ended Monday with the first-degree murder conviction of Dion R. Sobotker, 33.

“My son had gone through so much,” Harris said in an interview Tuesday.

Her son’s case, which dates to late 2014, was notable in large part for who he was: 26 years old, not much more than 100 pounds, and a survivor of open-heart surgery and two kidney transplants. His saga was featured several years ago as part of an NBC “Today” program about organ donation.

Dion R. Sobotker, 33, above, was convicted Monday in the slaying of Jonathan Harris. (Montgomery County Police)

Sobotker, of Temple Hills, is due back in court May 18 for sentencing.

Two others also were arrested in the case. Samantha Parker, who had dated the victim, died of natural causes, and Latoya Morgan previously pleaded guilty to being an accessory after the fact in a robbery that was part of the killing.

The three had driven to Jonathan Harris’s apartment in Silver Spring, according to police, and at least two went inside. The intruders stole items including two televisions and a Sony PlayStation, and used one of Harris’s credit cards to buy $30.89 worth of fast food. Harris’s blood later was found on one of Sobotker’s shoes.

Harris testified on Thursday, choking up early as she told prosecutor Patrick Mays her son’s date of birth: Jan. 30, 1988.

“My precious,” she said quietly.

Jonathan had only one kidney yet was in fairly good health until he was 12, when it failed. He was on dialysis for two years before his older brother gave him a kidney.

After that kidney failed, Jonathan took part in a program chronicled on the “Today” show. He was part of a transplant exchange program organized by three hospitals in the Washington area. His mother participated by donating a kidney to a stranger; another stranger donated a kidney to Jonathan.

In all, 32 people participated — 16 donors and 16 recipients. In an interview, Jonathan said his participation signaled an exciting new chapter in his life.

“I guess that just means I was put on this Earth for bigger things, better things,” he said.

Over the next several years, he flourished, his mother said from the witness stand. He was going to community college, delivering pizzas, and writing and performing rap music.

His mother had an apartment built in the basement of her home in Silver Spring — with a separate entrance — where Jonathan lived.

“We had a philosophy: Give the world the best you have, and the best will come back to you. That’s Jonathan and I,” Harris testified.

The morning of Dec. 6, 2014, she saw her son’s car still parked outside, which was odd, especially since he wasn’t answering his phone. She later went down to check on him.

“I came down the stairs,” she said. “The door was open, and as I walked in, Jonathan was lying on the floor.”

She called out his name.

“Jon! Jon! Jon!”

“I was trying to get some reaction,” Harris told the jury. “I didn’t get any.”

She called 911.

Mays halted her testimony to play a recording of the emergency call. Harris’s voice could be heard: “I need an ambulance, very quickly. My son, he has fallen.”

“Somebody robbed him. I can’t get him to wake up. . . . Oh, my God.”

Police and paramedics arrived.

Harris was outside, she told the jury, when she saw them take a medical bed inside.

“They came out with the gurney,” she said, “and it was empty.”