An illegal immigrant who was charged with drunken driving last year when he struck a car carrying three nuns, killing one and injuring the others, was convicted Monday of felony murder.

Carlos A. Martinelly-Montano’s case ignited outrage and prompted calls for stricter immigration enforcement.

During a hearing in Prince William Circuit Court, the facts of what happened Aug. 1, 2010, were not in dispute: Martinelly-Montano swerved his Subaru into a guardrail and then veered into the opposite lane on a slim, two-lane road in Bristow, colliding with the nuns’ blue Toyota.

Martinelly-Montano, who came to the United States from Bolivia as a child, had twice been convicted of driving under the influence in the years before the crash. At the time, he had been awaiting a deportation hearing for almost two years.

The nuns, who belonged to the Benedictine Sisters, were on their way from Richmond to Bristow for an annual retreat. Sister Denise Mosier was killed. Sisters Charlotte Lange and Connie Ruth Lupton, both in their 70s, were badly hurt.

Lange, the director of ministry at St. Mary’s Hospital in Richmond, was driving that morning. She testified that she had recently celebrated her 50th year as a nun and had the drive to the retreat down to a “science” — take Interstate 95 to Route 234. She saw the crash coming from a distance — the Subaru swerving into her lane — and realized, “I couldn’t come to the other side.”

The aftermath was a haze of hospital visits and therapy for both sisters. Lange has a metal plate in her right leg and has endured several surgeries on her stomach — a result of the seat belt’s impact, she said, among other injuries. It’s also affected her memory and hearing.

“I call it the ‘new normal,’ ” she said. “I’m back at work. I’m tough.”

Lupton lost her left thumb. She testified that her memory has deteriorated and her hand injuries have made everyday tasks difficult. She recently used a walker to get around and now uses a cane; she didn’t need assistance before, she said. Scars like “railroad tracks” climb up her back where pins hold together vertebrae, she said.

At the start of the court proceedings on Monday, Martinelly-Montano pleaded guilty to five charges stemming from the incident: involuntary manslaughter, two counts of maiming while driving under the influence, driving on a revoked license and a third DUI offense within five years.

But he went to trial before a judge on a charge of felony murder — unintentionally killing someone while committing a felony. Because the drunken-driving conviction was Martinelly-­Montano’s third, it is considered a felony under Virginia law.

Defense attorneys argued that Martinelly-Montano’s actions did not rise to the level of a felony murder, and that he could not be convicted of both manslaughter and felony murder.

In the end, Circuit Court Judge Lon E. Farris found Martinelly-Montano guilty in what prosecutors said was a rare instance of the charge being applied in a drunken-driving case.

Together, the charges carry a maximum sentence of 70 years in prison. Martinelly-Montano is scheduled to be sentenced Feb. 3. Defense attorney Melissa Sanchez said an appeal is likely.

Sister Cecilia Dwyer had been waiting for the sisters that day and was on the other end of a frantic phone call from Lange. Before testifying Monday, she looked at Martinelly-Montano and smiled. Family members said later that the sisters — who have publicly and privately offered forgiveness — have been writing letters to Martinelly-Montano and that he has since turned to the Bible. His mother, Maria Martinelly-Montano, said the Benedictine sisters have invited them over for dinner.

Asked outside the courtroom about her smile, Dwyer said that it was her “natural reaction” as an “extrovert.”

“I don’t know him,” she said. “It was benevolence.”