PEABODY – A Peabody man was sentenced to life in jail on Thursday for his conviction of threatening to kill an undercover Peabody police sergeant and robbed him in 2008.Earl Francis Hart, 50, was sentenced by Judge Patti B. Saris for brandishing a firearm in furtherance of a drug trafficking crime, being a felon in possession of a firearm, conspiracy to possess with intent to distribute oxycodone and attempted possession with intent to distribute oxycodone.Hart was found guilty of the above crimes by a federal jury in October 2010. The convictions stem from Sept. 18 and 19, 2008, when Hart, who had previously been convicted of a felony, conspired to possess with intent to distribute oxycodone, and then used and brandished a firearm with that offense.During the trial, evidence showed that on Sept. 19, 2008, at the Carriage House Motel on Route 1 North in Peabody, Hart racked a loaded Iver Johnson semiautomatic .380 caliber handgun, held it to the head of an undercover Peabody police department sergeant, threatened to kill him and then robbed the sergeant of what Hart thought was 125 oxycodone pills.Hart is also charged with witness tampering and witness retaliation stemming from a Nov. 24, 2009 incident, where he allegedly assaulted one of three co-defendants, Hector O’Brien, in the lockup inside the Moakley Federal Courthouse. All three of Hart’s co-defendants have pleaded guilty to the charges against them stemming from the September events in Peabody.During Hart’s sentencing on Thursday, Judge Saris discussed his length and violent criminal history, which began in 1979 when Hart was sentenced to nine years in San Quentin Prison for violently assaulting and robbing an elderly couple.Saris also said that her sentence was based on Hart’s lack of remorse and total refusal to accept any responsibility for holding a loaded gun to the head of a police officer.