Wollongong solicitor Katie Foreman had sex with her estranged boyfriend, Bradley Max Rawlinson, less than three days before he paid to have her killed, a court has heard.
Rawlinson, along with western Sydney couple Michelle Sharon Proud and Bernard Justin Spicer, are on trial in the NSW Supreme Court, accused of organising to deliberately set fire to Ms Foreman's Corrimal home in October 2011.
Jurors on Monday were told a semen swab taken from Ms Foreman just hours after she perished in the blaze matched Rawlinson's DNA profile.
During initial questioning from Crown prosecutor Chris Maxwell, QC, forensic biologist Sienna Collins estimated sex between the pair had occurred sometime between 48 and 72 hours prior to Ms Foreman's death but later revised that estimate to no less than 24 hours (before death) on further questioning.
"I don't expect it occurred [less than] 24 hours before but anything above 24 hours [is possible]," Ms Collins said.
"So it's fair to say Mr Rawlinson and the deceased lady had sex 24 to 48 hours prior to her death?" Rawlinson's lawyer, Winston Terracini, SC, asked.
"Yes," Ms Collins replied.
Another forensic specialist, Suzanna Djulamerovic, told the court swabs taken from Rawlinson's left and right hands less than 12 hours after the fire was lit did not test positive for any ignitable liquids. She said several other items and samples taken from Ms Foreman's room did test positive for petrol, including carpet and underlay samples from various points inside the room, as well as the remains of a sock and pink fabric recovered from Ms Foreman's body after her death.
However, she said samples taken from the north-east corner of the room, near the foot of the bed, did not test positive for any accelerants.
Earlier in the day, jurors heard from the head fire investigator on the case, Superintendent Robert Alexander, who identified the foot of the bed and the bedhead as the two most intense areas of fire within the room, based on burn patterns and the extent of damage to the bedroom furniture.
The jury was shown footage of the charred remains of the home during a 35-minute "walk through" video featuring Supt Alexander and homicide squad detective Stephen Hungerford.
The footage lays bare the extensive damage caused by the fire, which was contained to Ms Foreman's upstairs bedroom, and the resulting smoke, heat and water damage throughout the house.
Giving evidence on Monday, Supt Alexander said when he entered the room, he detected a "faint" smell of petrol, however, that smell became more pronounced as the charred rubble and burnt furniture was removed from the room.
He estimated the temperature of the fire was between 500 and 600 degrees, based on melting aluminium found on the window sill.
The trial continues.