A Superior Court judge agreed yesterday to release Alexander Pring-Wilson on $400,000 bail, reversing a lower court decision that had kept the Harvard graduate student in jail since his April 12 arrest on murder charges.

Pring-Wilson—who will be placed under house arrest and monitored with an electronic device—was expected to post bail this morning.

A 25-year-old graduate student who was set to earn his master’s degree from Harvard’s Davis Center for Russian and Eurasian Studies this spring, Pring-Wilson is charged with first degree murder for stabbing and killing Michael D. Colono, an 18-year-old Cambridge resident.

Pring-Wilson stood expressionless as Middlesex County Superior Court Judge Geraldine Hines delivered yesterday’s ruling, which reversed an April 18 district court decision to deny bail to Pring-Wilson.

Assistant District Attorney Adrienne Lynch argued yesterday that the court should once again deny Pring-Wilson’s request for bail, due to “the serious nature of the crime, the strength of the government’s case and the flight risk [Pring-Wilson] poses given his resources.”

The lower court judge had ruled that these specific factors justified keeping Pring-Wilson behind bars while awaiting trial.

But Hines said yesterday that she was not convinced. Pring-Wilson is unlikely to flee, she said.

Hines added however, that her decision was not colored by Pring-Wilson’s education and financial background. Family, friends and Harvard acquaintances had vouched on Pring-Wilson’s behalf, while prosecutors argued that his travel experience and knowledge of several languages made him a flight risk,

“It’s not about the defendant’s class. I’m not impressed with the fact that it is a Harvard student,” Hines said. She added, however, that she was confident he would make required court appearances.

Hines imposed several conditions in her ruling.

Allowed to leave his Somerville apartment only to meet with his attorney or doctors, Pring-Wilson must also meet weekly with a probation officer, avoid drug use and alcohol consumption, surrender his passport and maintain no contact with witnesses in the case. He must stay in Massachusetts for the duration of the trial unless he obtains special permission from the court, Hines ruled yesterday.

While about a dozen friends and family of Colono, the slain Cambridge teen, looked on with disappointment during the ruling, those close to Pring-Wilson embraced each other with relief outside the packed courtroom.

Denner said his client will help prepare his own defense and continue to work on his thesis about the reconstruction of post-war Bosnia, in the apartment he shares with two other students near Davis Square.

Denner, who told the court that Pring-Wilson’s family had already collected $300,000 for bail, said Pring-Wilson has taken a voluntarily leave of absence from Harvard and will not graduate as planned this spring.

Both Pring-Wilson’s mother, Cynthia M. Pring, and father, Ross A. Wilson, are Colorado attorneys and will help in their son’s defense.