Mr Fiannaca told the court that Schmidt, in a "fit of rage" had pushed Mr Marshall, 29, so hard he crashed through the window and fell five metres. He suffered fatal head and chest injuries.
CCTV footage from inside the hotel before the incident and of Mr Marshall landing on the footpath outside was played to the court.
Schmidt could be seen walking out of the hotel and glancing towards where Mr Marshall lay before disappearing.
Mr Fiannaca said text messages sent by Schmidt to a friend and his girlfriend would show he was not shocked by the incident, the West Australian reported.
Schmidt's retrial was ordered after the Appeal Court ruled there had been a miscarriage of justice because the trial judge did not adequately direct the jury on an essential element of the case against Schmidt.
Mr Marshall is the cousin of Feilding farmer Scott Guy, who was shot dead at the end of his driveway in July 2010.
Mr Marshall's parents Alan and Wendy, from Hawkes Bay, are expected to be at Schmidt's retrial, telling APNZ last month they were unsure what to expect this time around.
"You try to keep your mind open and deal with it one day at a time. You never stop being a parent. You're always a parent in life and death," Mr Marshall said.
"You don't stop feeling or loving your own children and I guess that's the price you pay in some ways for that relationship and that depth of love.
He expected more focus this time on his son's injuries and pathology evidence, as was alluded to in the Appeal Court ruling.