He will be sentenced on March 13 and the Crown will seek preventive detention.
The police summary of facts was released to the Herald after today's hearing, revealing for the first time the specific details of Tian's violent death.
Stroobant lived over the back fence from where Tian lived with her daughter and son-in-law on Glenvil Lane.
Police at the scene of the Glenvil Lane house. Photo / Jason Oxenham
"On Friday 15 January 2016 the victim was at home alone. As was typical of any week day her daughter and son-in-law left home at around 9am to work in the city. The victim began her usual gardening tasks around the home," the court document stated.
Stroobant was also home that day and sometime during the morning he went to Tian's property.
"[Stroobant] entered the property and confronted the victim," the summary read.
"He grabbed her and dragged her before violently physically and sexually assaulting her."
While Tian was on the ground, Stroobant struck her around the head "numerous times".
"During the assault he stood up and stomped on her face and head," police said.
"This caused the fatal head injuries that eventually killed her."
Stroobant pulled down Tian's trousers and underwear and sexually violated her.
"At the time of the violations the victim was alive, unconscious and dying from the injuries inflicted," the summary said.
"The pathology indicated that the victim sustained a severe assault with evident of blunt force trauma to her head, face, neck, chest, [genitals] and lower limbs.
"The effects of the head injuries caused the victim's death."
Specific details of the sexual violation charges are suppressed as Stroobant claims publication of the details could put him in danger in prison.
Police at the scene on Glenvil Lane. Photo / Jason Oxenham
The Crown, Tian's family and the Herald will be opposing the suppression order, and Justice Graham Lang will make a final decision on publication at sentencing next month.
A post-mortem examination revealed that Tian suffered extensive bruising to the head and face as well as numerous cuts and abrasions.
She had blood clots on her brain, which was "significantly" swollen, and a fractured right eye socket.
Tian also had bruise marks on her neck that were consistent with Stroobant "restraining her from behind".
She had multiple broken bones including one in her neck and ribs and extensive injuries to her genitals.
He stole an iPad, Chinese currency that he later exchanged for NZ$370, and a gold watch belonging to Tian's daughter.
"[Stroobant] then made efforts to evade detection by police, staying at a friend's address overnight, dismantling his phone by removing the SIM card and battery and riding in the boot of his friend's car," the summary stated.
When police finally caught up with Stroobant at an Auckland house he tried to flee through a back window.
Detectives interviewed Stroobant, who denied any involvement.
Soon after his arrest a woman was arrested and charged with being an accessory after the fact of Tian's murder.
