Madeleine Pulver speaks outside a court in Sydney after her attacker is sentenced to 13 years in prison Reuters

An Australian investment banker who admitted chaining a fake bomb to a Sydney teenager as part of a bizarre extortion plot has been sentenced to 13 years and six months in prison.

Madeleine Pulver, then 18, was studying at home alone in her family's mansion in August 2011 when Paul Douglas Peters walked in wearing a rainbow-striped ski mask and carrying a baseball bat. He tethered a bomb-like device to her neck along with a ransom note and then slipped away. It took a bomb squad 10 hours to remove the device, which contained no explosives.

Peters, 52, failed to convince the judge his crime was the result of a psychological meltdown sparked by the breakdown of his marriage and a failing career. Instead, the judge said, the once-successful businessman and father of three had shown no remorse, lied to police and was largely motivated by money.

"The offender intended to place the very young victim in fear that she would be killed," New South Wales state district court judge Peter Zahra said. "The terror instilled can only be described as unimaginable."

Pulver hugged relatives after the sentence was read. Her father, Bill Pulver, wiped away tears.

"I'm pleased at today's outcome and that I can now look to a future without Paul Peters' name being linked to mine," Madeleine Pulver said outside court.

"For me, it was never about the sentencing, but to know that he will not re-offend. And it was good to hear the judge acknowledge the trauma he has put my family and me through."

Zahra gave Peters less than the maximum sentence of 20 years, acknowledging he had pleaded guilty and was likely depressed at the time.

After attaching the device to the teen, Peters fled to the US, but police used an email address he left on the ransom note to track him down. Authorities arrested him two weeks later at his ex-wife's home in Louisville, Kentucky, and extradited him to Australia. He pleaded guilty in March to aggravated break and enter and committing a serious indictable offense.

Defence lawyers had argued that Peters was depressed, drinking heavily and exhibiting wild mood swings before committing the crime and had no memory of the attack. He had recently split from his wife, was separated from his children and had become obsessed with a book he was writing about a villain out for revenge, his lawyer, Tim Game, said during earlier sentencing hearings.

A psychiatrist for the defence testified that Peters may have tried to become the evil protagonist in his book. Peters told the psychiatrist: "It's not about money, it's about revenge."

But prosecutors disagreed. During an earlier hearing, prosecutor Margaret Cunneen said Pulver was never the intended target of Peters's crime. The investment banker was having financial problems and originally travelled to Mosman, the wealthy Sydney suburb where the Pulvers live, to hunt down the beneficiary of a multimillion-dollar trust fund he had learned about, she said. When he arrived in Mosman, he bumped into a neighbour of the Pulvers, whom he had met while doing business in Hong Kong. That man, who lived next door to the Pulvers, then became Peters's new target, Cunneen said.

But on the day of the attack, Peters walked into the wrong house. Madeleine Pulver was the unwitting victim of Peters's incompetence, the prosecutor said.

Embarrassed by his bungled extortion bid, Peters concocted a story about being delusional and not remembering the crime to save face, Cunneen said.

The judge largely agreed with the prosecution's version of events, saying the attack was precise and premeditated, and dismissed the defence's arguments that Peters was delusional and in a psychotic state during the crime. Zahra did accept that Peters was likely depressed, but said it did not explain or excuse his behaviour.

Peters, who will be eligible for parole in 10 years, cried in court when the judge detailed the problems the banker had been facing with his marriage and his career. He showed no emotion when the judge described the trauma Madeleine endured as a result of the attack.

"Mr Peters has actually, from our perspective, shown no clear remorse for this entire event," Pulver said outside court. "There has still been no apology nor any explanation for his behaviour, which is disappointing. But the man was just told he was going to be in jail for 10 years, so he has reason to be upset."