While there was blood spatter on the floor, ceiling and furniture, she also identified two areas on the walls where there were wipe marks.
A bottle of lavender disinfectant found on the kitchen table also had blood on the handle, the court heard.
Crown prosecutor Pip Norman in her opening address on Monday said clean-up efforts appeared to have been quickly abandoned as a "futile endeavour" before the address was vacated.
Rough identified three impact sites in distinct areas of the cramped lounge.
Two of them, she said, likely came at a height of less than 50cm.
Photos of the living room showed a large patch of blood in the middle of the floor along with skin and bone fragments.
It was evidence of significant damage to Bacon's head, said Rough.
Among it all were the victim's bloodstained jandals.
She was cross-examined by Len Andersen QC about whether the presence of a third person would change her conclusions.
While Rough maintained her stance, she acknowledged there were many variables involved in her work.
After the incident, it is accepted Collins, and his partner 32-year-old Aleisha Dawson, forced the victim's body into a blue sleeping bag, loaded it into his Toyota people-mover and dumped it under a tree beside a rural road off State Highway 1 north of Dunedin.
It was noticed by a cyclist two weeks after the alleged murder, and just hours after the scene at 47 Lock St was discovered.
The court earlier heard Bacon had moved to Dunedin to live with his sister and brother-in-law Lia and Sam Bezett, following years of drug and mental-health struggles.
The victim knew Collins and Dawson from when he lived in Christchurch and would often spend evenings at their Lock St home, where they had resided from November 2018.
After fleeing north after the incident, the pair sold Bacon's car to a backpackers and got a ferry to the North Island.
They were found by police on February 20 in a car park in Rotorua.
Collins told interviewers Bacon had been paranoid on February 4 and "came at him", fist raised and looking angry.
He described using the bat overarm "like swinging an axe" but said he did not intend to hit Bacon.
The defendant said he hit him perhaps twice more before but could remember no more because he "blacked out".
Andersen said his client had no murderous intent.
Bacon suffered fractures to his skull and face, as well as broken bones in his hands which Norman said were consistent with defensive injuries.
Dawson pleaded guilty and was earlier sentenced as an accessory to homicide.
The trial, before Justice Jan-Marie Doogue, will hear today from medical witnesses who examined Bacon.
