CHICAGO >> A federal jury convicted a registered sex offender from Aurora, Illinois Thursday of groping a woman as she napped last year on a flight from Las Vegas after celebrating her 34th anniversary with her husband.

Prosecutors said it marked Srinivasa Erramilli’s third conviction for the same offense since 1999.

The jury deliberated about three hours before convicting the Indian national, 45, of abusive sexual contact on an aircraft. He faces up to two years in prison and possible deportation on his release. Immigration authorities will consider if the software consultant overstayed his visa, authorities said. He is working in the U.S. on a work permit.

“This case was allowed to be successfully prosecuted because of the willingness of the victim to speak up and not dismiss what happened, which was a serious offense,” said Randall Samborn, a spokesman for the U.S. Attorney’s Office in Chicago.

Erramilli was sentenced to probation in 2000 after he was convicted in Cook County court of fondling the breast of a woman who sat in front of him on a flight from Detroit to Chicago the year earlier, authorities said. In 2002 he was sentenced in federal court in Detroit to three years’ probation after he was convicted of abusive sexual contact for groping the breast of another woman aboard a flight from San Jose, Calif., to Detroit.

Prosecutors said Erramilli was the last passenger to board a Southwest Airlines flight to Chicago’s Midway Airport in June 2011 and was seated in the only vacant seat – between the victim, who had chosen a window seat to sleep, and her husband, who took the aisle seat for easier access.

The victim, who was wearing shorts, told the jury that she was awakened twice on the flight, first when she felt something brush against her thigh and then when she felt pressure on her thigh. But she was uncertain of what had happened. She then closed her eyes but did not fall asleep. Erramilli reached underneath the leg of her shorts and rubbed and grabbed her thigh, she said.

She testified that she struck Erramilli several times and called him a “pig or a pervert.”

During her testimony, the woman demonstrated how Erramilli grabbed at her with the assistance of a federal prosecutor as both sat in chairs in front of the jury. Other passengers and flight attendants also testified during the trial.

On Thursday, after word of the verdict, Erramilli appeared nervous while waiting for the jury in the courtroom. He showed little reaction at word of his guilt but minutes later dropped his head into his hands and slumped back in the chair.

Prosecutors sought to have Erramilli taken into custody on his conviction, but U.S. District Judge Joan Lefkow allowed him to remain free until his sentencing, scheduled for April 26.