Before the gears of a third trial could begin to turn, Alexander Pring-Wilson pleaded guilty to involuntary manslaughter Friday. He was sentenced to two years and one day in prison.

Pring-Wilson was a graduate student at the Davis Center for Russian and Eurasian Studies in 2003 when he stabbed Cambridge resident Michael D. Colono to death in a chance encounter.

The former Harvard student has already served 290 days since 2003 for a stabbing that he characterized as self-defense after Colono’s teasing led to a fight.

Cynthia M. Pring, the mother of Pring-Wilson, expressed disappointment with the outcome.

“I know my son acted in self-defense,” she said.

Pring explained that being under house arrest has been difficult for her son and that the “finality” and relief from the legal costs associated with avoiding a third trial had influenced the plea decision.

“It’s very frustrating—ultimately not what we would hope,” she said.

Peter T. Elikann, a Boston criminal defense attorney, called the verdict a “compromise.”

“It leaves both sides empty in a way,” he said, noting that Pring-Wilson, though now a convicted killer, received a relatively light sentence. He said that going through a third trial would have been a risky prospect for the defense.

“There really are no winners here,” Elikann said.

Natalia Pokrovsky, a former Slavic languages preceptor who taught Pring-Wilson, said she agreed with his decision for a plea bargain. “In a year it will be over. It will be behind him. I think that he did the right thing,” she said.

Pring-Wilson was convicted of manslaughter in October 2004 and sentenced to six to eight years in prison. In 2005, Pring-Wilson was granted a retrial after the Massachusetts Supreme Judicial Court ruled that evidence of a victim’s violent history could be used in self-defense cases.

That trial resulted in a hung jury last month. Middlesex District Attorney Gerard T. Leone Jr. ’85 had promised to pursue a third trial before the plea bargain was struck.

Ada Colono, the victim’s mother, declined to comment. Leone’s office and Pring-Wilson’s lawyer could not be reached for comment.

—Staff writer Lingbo Li can be reached at lingboli@fas.harvard.edu.