It is an alleged murder without a body, but the Crown argues circumstantial evidence is enough to convict accused killer James Scott Church.
Leisl Smith, 23, was last seen leaving her home at Wallarah on the New South Wales Central Coast on August 19, 2012.
Her car was found abandoned at Tuggerah railway station and CCTV captured her getting into a white utility that then drove away.
The NSW Supreme Court has heard that ute belonged to her ex-boyfriend, James Scott Church, known as Jim Church.
Mr Church, 51, has pleaded not guilty to murder in a judge-only trial before Justice Elizabeth Fullerton.
Ms Smith's body has never been found.
In her opening address this week, Crown prosecutor Kate Ratcliffe said the evidence would show Mr Church was her killer.
"It is the Crown case that this accused was responsible for arranging for Ms Smith to meet him and get into his utility under false pretences," she said.
"He drove up the M1, through the Lower Hunter, along the Golden Highway and through Sandy Hollow and Merriwa.
"At some time during the journey he killed her and disposed of her body.
"The Crown case is wholly circumstantial and the place she met her death is unknown and the manner and cause of death is unknown.
'Best cowboy in the country'
Mr Church was a farrier and respected horseman who shared a love for the animals with Ms Smith.
The Crown alleges their mutual passion led to a sexual relationship, pregnancy and ultimately her death.
The court heard that at the time Mr Church had begun a relationship with a woman whose family had made millions of dollars from property developments.
Ms Ratcliffe said Mr Church had asked his younger lover to terminate her pregnancy but she refused and he feared for his reputation.
"The relationship [with Leisl] caused problems in accused relationship with [the other woman], who was a wealthy and attractive woman," she said.
The prosecutor said when Ms Smith learned of that relationship she was distraught and sent text messages to the other woman.
"She made threats to burn her house down and made claims she was carrying the best cowboy in the country's child," Ms Ratcliffe said.
Accused allegedly scouted burial site
Mr Church told police he dropped Ms Smith off at Wyong on the day she was last seen and never saw her again.
But the Crown said a time-stamp from a fixed camera on the M1 Pacific Motorway showed his vehicle was travelling north at that time, towards the Hunter region.
Ms Ratcliffe said the route was known to Mr Church and told the court he had travelled the same way two days before to scout out a site at which to bury Ms Smith.
"The Crown says … on that day, leaving very early in morning, at around 5:30, the accused left his home," she said.
"He then drove to a remote location around Merriwa in order to locate a site where he would dispose of the body of Miss Smith, who he was planning to murder."
At that point Justice Fullerton asked if Ms Ratcliffe was alleging the journey to be a reconnaissance trip, to which the prosecutor replied, "Yes".
The court heard police asked Mr Church about that trip before his 2018 arrest.
Ms Ratcliffe said Mr Church told police he made the journey to see a friend about horse-related matters and later asked that same friend to provide a false alibi.
Defence barrister Manny Conditsis will deliver his opening address on Wednesday.
There are more than 300 potential witnesses.
Justice Fullerton has indicated that she expects the trial to run for six to eight weeks.
