German national Mr Brueckner had been charged with three counts of rape and two counts of sexual abuse, with the court hearing testimony from Ms Behan, who testified that she was threatened and raped by a man who broke into her Algarve apartment in 2004 and she believed Mr Brueckner was the perpetrator.
He had been on trial since February over the offences he is alleged to have committed in Portugal between 2000 and 2017.
He was fully acquitted after an eight-month trial, with the judge presiding over the case telling the court yesterday that there was insufficient evidence to convict Mr Brueckner.
Ms Behan told ITV in the aftermath of the verdict, which prosecutors have said they will appeal at the Federal Court of Justice to seek a retrial, that she was “shattered”.
“I’m shattered. I’m really, really broken,” she said.
In May, Ms Behan, who is originally from Westmeath, told Brueckner’s trial she felt a “fear that I could never ever put into words” after being woken by a masked stranger who carried out the attack on her in 2004.
Ms Behan (40) sat just metres from Brueckner in court and had previously waived her anonymity.
Judge Engemann said the evidence “was not enough” to convict Mr Brueckner, who is currently serving a seven-year sentence for an unrelated rape charge and could now be released from prison next September.
Prosecutors in the latest case had recommended that he should be jailed for 15 years.
Brueckner was also accused of raping a teenage girl in his Praia da Luz home and raping an elderly woman in her holiday apartment. He faced child sex charges for allegedly exposing himself to a German girl on a beach in Salema in April 2007 and an alleged indecent exposure in front of an 11-year-old in 2017.
He was convicted in 2019 for the rape of a 72-year-old American woman in Portugal in 2005.
Mr Brueckner is considered the chief suspect in the case of Madeline McCann, though he has not been charged.
He spent many years in Portugal, including in the resort of Praia da Luz around the time of Madeleine’s disappearance there in 2007. He has denied any involvement in her disappearance.
McCann disappeared from her bedroom on May 3, 2007, during a family holiday while her parents were dining with friends nearby in the resort of Praia da Luz.