Throughout the day a group of Chinese men were parked conspicuously in front a fire hydrant outside, breaking a basic American road law and suggesting they were unfamiliar with the country's rules.

Mr Bo's father, a charismatic senior Chinese politician once tipped as a future premier, was purged by the ruling Communist party this week while his mother, Gu Kailai, was detained on suspicion of murder.

She is accused of plotting the killing of Neil Heywood, a 41-year-old British expatriate and former confidante, whose death in a hotel room last year was initially blamed on alcohol poisoning.

Mrs Bo is suspected of "intentional homicide", while Mr Bo is accused of "serious discipline violations", in the severest crisis to grip China's secretive ruling elite in decades.

The author of America's asylum law said their son, who like his mother is said by Chinese officials to have fallen out with Mr Heywood over money, had a compelling case for refuge in the US.

"If you can establish there's a well-founded fear you would be persecuted in China because you would be imputed with the subversive or corrupt political views of your father, you would be just as eligible for asylum," said Bruce Einhorn, a retired judge and professor at Pepperdine University.

As Mr Bo is in the US legally on a student visa, he could apply for asylum "affirmatively" without being put into deportation proceedings. Due to the high-profile nature of the case, officials in Boston could pass any decision up to Alejandro Mayorkas, President Barack Obama's immigration chief.

Officials are not supposed to consider potential diplomatic impact, but experts said it would be impossible to ignore the fact that it would be a "political hot potato" between the US and a rival power.

"Legally it would be pretty straightforward," said Prof. Kevin Johnson, the dean of University of California's law school and an immigration expert. "But politically it would be complicated".

However one of Mr Bo's closest friends told The Daily Telegraph he would be determined to return to China to serve his country, which he has said he wants to keep on a "path of smooth transition".

"He wants to go back to help," said the friend, who holidayed with Mr Bo and his parents. "He wanted to serve China in some way. The only thing he cared about, everything, referred to his country."

The friend said Mr Bo respected his father and deeply admired his grandfather, Bo Yibo, who was one of Chairman Mao's eight "immortals" of the Chinese Communists' revolutionary generation.

Describing Mr Bo's parents as "extremely kind and generous", the friend said: "When you think about Chinese parents, they are not typical. They are very international and multicultural."

Mr Bo has been studying for a $90,000 (£56,610) Master's in Public Policy at Harvard's prestigious Kennedy School of Government since 2010 and was due to begin his final exams at the start of May.

He is said to have taken a more serious approach to his studies since being embarrassed by leaked pictures of parties at Oxford, from which he graduated only after being disciplined for poor work.

Harvard peers said Mr Bo, who retains a slight English accent, often spoke in classes about China but would dodge questions about its lack of democratic reform.

"He was very sociable in his first year and hosted a number of parties but he's been much lower-profile this year," said one student.

He lives in a luxurious two-bedroom flat on the ground floor of a seven-storey building near campus that features a doorman, gym and roof sundeck, paying $2,950 per month in rent.