"Mr Lavemai, you brutally murdered a truly beautiful man, a man who simply wished to live his days in peace, a man who never took but only gave," Ms Lees said.
"Richard's life and love of life will live forever in our hearts, whereas your heart is dead," she told Lavemai.
Ms Lees thanked the detectives who worked on the case, the Crown and the Sensible Sentencing Trust for supporting her.
Mr Lees was struck about the head and neck about 11 times by Lavemai.
On October 12, 2012, Lavemai spent the day drinking and possibly using P. He owed money over a drug debt so decided to steal items from his neighbour's property, where Mr Lees was staying temporarily.
That evening Lavemai knocked on Mr Lees' door. "He was polite and invited you in. Without warning and without any provocation on Mr Lees' part, you punched him almost immediately," Justice Murray Gilbert told Lavemai.
The first blow landed Mr Lees on the couch and he soon lost consciousness, but Lavemai kept punching.
He later told friends this gave him a thrill. "You said there was a voice telling you, 'don't stop, just carry on'."
As Mr Lees was struggling for breath, Lavemai stole a PlayStation and a stereo. He made no attempt to help the dying man, who was found the next day by his friends.
"This murder was committed with a high level of brutality and callousness," Justice Gilbert said.
Defence lawyer Kelly-Ann Stoikoff said Lavemai, who was initially in denial about what he did, offered his "heartfelt and sincere" apologies to Mr Lees' family.
"The truth is Mr Lavemai was scared to admit the reality, even to himself. Since the guilty verdict Mr Lavemai has come to accept not only the reality but the enormity of what he has done."
Lavemai had only minor previous convictions, was undertaking rehabilitation courses and had become his prison unit's union rep.
A pre-sentence report said his mother died when he was young, he had little contact with his father and along with his siblings, moved between foster homes.
Lavemai was also convicted of theft for stealing the electronic items.