BOSTON (AP) — An FBI agent overheard Boston Marathon bombing suspect Dzhokhar Tsarnaev make a "statement to his detriment" when his sister visited him in prison, federal prosecutors said Friday. Prosecutors did not reveal what Tsarnaev said, but they objected to what they called an attempt by Tsarnaev's lawyers to suppress the statement.... [snip] Tsarnaev, 20, has pleaded not guilty in the terrorist attack at last year's marathon. Two pressure cooker bombs were placed near the marathon finish line, killing three people and wounding more than 260.... [snip] Tsarnaev's lawyers say the presence of the FBI agent during prison visits...