A forensic pathologist was unable to determine Bradley Breward's cause of death because of the state of decomposition his body was in, a jury has heard.
Mark Rodney Jones has pleaded not guilty to murdering Mr Breward at a Newnham unit on New Year's Day in 2017.
Forensic Pathologist Dr Donald Ritchie gave evidence on the fifth day of the Launceston Supreme Court trial.
The court heard Mr Breward's body was dumped at Lake Eugenana on the day he was killed, but was not recovered by police divers until more than a month later on February 3.
Dr Ritchie told the court Mr Breward's body was in a moderately advanced state of decomposition, with soft tissue missing from his neck and chest.
Dr Ritchie said during his examination he found Mr Breward's heart and lungs had liquified, weighing 20 grams and 15 grams respectively.
"They were so decomposed that grossly and under the microscope I was unable to make any findings," Dr Ritchie said.
The court also heard Mr Breward had two transverse rib fractures with one on each side of his chest.
Dr Ritchie said it wasn't possible to say for certain when the fractures occurred, but callus tissue would build up after a week if it was healing and there was no tissue on Mr Breward's injuries.