The court released a transcript of the recorded telephone conversation Wednesday. Mazzaglia is scheduled to be sentenced Thursday for the murder of Elizabeth "Lizzi" Marriott.
During the Aug. 6 call, Mazzaglia told his mother, Heather, the hearing will be "a waste of my time."
"I'm gonna have to sit there for an hour and a half listening to them yell and whine and bitch and moan and scream about how I'm a monster," he said.
Heather Mazzaglia urged her son to empathize with Marriott's family, saying she would feel as they do if something had happened to him.
Marriott, 19, disappeared in October 2012. Kathryn McDonough, Mazzaglia's former girlfriend, testified he killed Marriott, 19, of Westboro, Mass., when she refused to continue a game of strip poker.
McDonough, who is serving a three-year prison term, admitted she helped Mazzaglia get rid of the body by packing it in a suitcase and throwing it into the Piscataqua River estuary in Portsmouth, N.H. Marriott's body was never found.
Mazzaglia faces a sentence of life with no parole.