Because Unterweger had lied to get into the US, he could technically be arrested for this alone. When Mrak’s mother wired some money to her daughter, US marshals saw this as an opportunity to arrest him at a Western Union office in South Beach, California.
After Mrak collected the money she and Unterwegger walked out of the building while the marshals followed. But Unterweger twigged something was up and bolted. He was chased through a restaurant, but finally cornered in a back parking bay, handcuffed and arrested. It is alleged that when the police officers informed him he was wanted for murders in Austria, Unterweger broke down and wept.
A search of Unterweger and Mrak’s Malibu apartment revealed many incriminating items that could be linked to the murdered LA prostitutes. The police also recovered a diary written by Unterweger which suggested he had plans to dispose of Mrak.
Unterweger preferred to be tried in California as he knew that he would be facing a charge of murder against just three victims as opposed to many in Austria. However, realising that he could also be facing the gas chamber he quickly agreed to extradition. Unterweger was deported on the 28 May 1992.
Unterweger played on logic to defend himself. Why as he pointed out would a man such as himself, who had been rewarded so well with fame and money, suddenly decide to destroy his privileged life by murdering women?
But before the court case commenced, Dr Geiger enlisted Thomas Mueller, Chief of the Criminal Psychology Service in the Federal Ministry of the Interior, to accompany him to America and learn all they could about the psychology of compulsive serial killers.
Through a briefing with the Behavioural Science Unit (BSU) at Quantico, Virginia, Geiger and Mueller discovered that there were standard forms of behaviour relating to murderers like Unterweger, who also displayed deviant sexual obsessions that usually followed a pattern. Although most serial killers rarely move from one country to another the details of the deaths of the Los Angeles prostitutes were too close to those in Austria to be purely coincidental.
But there was more tangible evidence to come against Unterweger when analysis on the knots to tie ligatures on the three Los Angeles prostitutes, matched the pantyhose knots used on the victims in Austria.