A little more than a year ago, Belinda Nguyen found her 12-year-old sister dead in the basement of their Gaithersburg home, the victim of a brutal stabbing.

On Wednesday, she said, she took some solace in knowing that Jessica Nguyen’s killer faces a long prison sentence. A Montgomery County Circuit Court jury had just convicted David R. Hang, who once was married to Jessica and Belinda’s mother, of first-degree murder.

“I’m glad they found him responsible and my sister’s death will be avenged,” Belinda Nguyen said.

Prosecutors said Hang, 43, attacked Jessica after becoming angry and frustrated with the girl’s mother and her adult relatives.

Jessica’s mother, Khen Kim Vu, who emigrated from Vietnam, had entered a sham marriage with Hang in 2006 in a bid to gain citizenship. After a while, Hang wanted out, prosecutors said. But they said he had difficulty extricating himself, complicating his efforts to get health insurance for a new girlfriend who was struggling with illness.

Jessica Nguyen, 12 killed in Gaithersburg. (Courtesy of Montgomery County Schools)

Prosecutors said Vu’s family had helped arrange the marriage and was involved in the later dispute.

Vu and Hang eventually reached a divorce settlement, and Hang’s attorney said he “did the right thing” and bought insurance for his companion himself. But prosecutors argued that Hang remained unhappy with the terms of the divorce and that the difficulties continued to weigh heavily on him.

“The defendant had money problems, relationship problems, medical problems. You talk about pressure every which way,” Assistant State’s Attorney Stephen Chaikin told jurors. The result, he said, was murder.

In his closing argument, Chaikin showed jurors a photograph of Jessica’s body. Prosecutors said she had been stabbed and cut more than 40 times with a small sword.

“This was personal,” Chaikin said, before later walking close to Hang and telling the jury: “Hold this monster accountable.”

But Montgomery public defender Brian Shefferman told jurors that Hang, who had worked as a Ride On bus driver, was “a peaceful person with no history of violence.” While his client had concerns about the health-insurance issue, he said, “it wasn’t driving him to do anything violent.”

Shefferman said Hang was at a doctor’s appointment in Virginia with his companion when Jessica was killed. He speculated that she could have been attacked by a burglar or a stranger interested in girls.

“David Hang is not the right person. He did not commit the crime,” Shefferman told jurors. “He had no reason to harm Jessica Nguyen. He did not harm Jessica Nguyen.”

During a week-long trial, prosecutors said several pieces of evidence linked Hang to the killing, while Shefferman dismissed the state’s case as “assumptions, speculation and guesswork.”

Although a murder weapon was never found, prosecutors showed the jury a sheath found at the scene that they said had been used to cover the weapon. The sheath had Hang’s DNA on it, but not that of other family members, Chaikin told the jury. Shefferman said DNA from other people was also found on the sheath.

Chaikin pointed to cellphone records that showed Hang was near the murder scene at the time of the attack. The defense challenged the reliability of those records.

The two sides also clashed over a bloody boot print found near Jessica’s body, which prosecutors said was from the type of boot that had been issued to Ride On bus drivers.

The prosecution said the defendant disposed of his boots after the crime. The defense said that Hang generally didn’t wear the boots and that his current wife had gotten rid of them. But that failed to sway the jury.

Jurors also heard about Jessica, an honor student at Gaithersburg Middle School. Vu wept as prosecutors showed Jessica’s school photo. Belinda Nguyen said she and her sister often tuned in to reruns of “Ghost Whisperer” on TV after school.

Belinda Nguyen, 18, testified about the last day she saw her sister alive. She told jurors she came home from school with Jessica on May 31, 2011, and decided to take a nap before starting an AP English project. Jessica popped into her room, she said, and teased her because she was texting with friends instead of studying.

In the late evening, Belinda Nguyen went down to the basement to look for Jessica.

“[Jessica’s] eyes were open. There was no movement, there was blood everywhere,” Belinda said. “I panicked and went to call 911.”

Hang is scheduled to be sentenced in October. After the trial, Hoa Dinh, Jessica’s uncle, spoke on behalf of the family.

“While nothing will bring back our Jessica, we have to find a way to move on with our lives,” he said.