Bo Guagua, son of fallen Chinese politician Bo Xilai, receives his masters degree in public policy at the John F. Kennedy School of Government during the 361st Commencement Exercises at Harvard University in Cambridge, Massachusetts in this May 24, 2012 file photograph. The son of Xilai has broken his silence and submitted a witness statement to the murder trial of his mother, CNN said on Wednesday, citing an e-mail from the young man.