Sweden’s Josef Fritzl – Martin Trenneborg

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23rd June 2022  •  5 min read

Martin Trenneborg claimed he was a rich American stockbroker when he struck up a relationship with a woman in Stockholm, Sweden. What the woman didn't know was that for years, Trenneborg had been building a secret bunker.

Sweden's Josef Fritzl - Martin Trenneborg

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In 2015, a woman from Stockholm, Sweden, struck up a relationship with 38-year-old Martin Trenneborg. The duo chatted over the phone, during which Trenneborg claimed that he was a rich American stockbroker based in London.

The woman was impressed. She invited Trenneborg over to her flat on the 10th of September, 2015. They spent the evening chatting, and the woman agreed to have a second date with Trenneborg.

On the 15th of September, the woman invited Trenneborg over to her flat once again. When she opened the door, Trenneborg presented her with champagne and chocolate-dipped strawberries. The duo sat down on the couch, and began to eat and drink.

Trenneborg was not actually an American stockbroker. He had a successful career as a doctor, which was just as impressive. However, there was a reason that Trenneborg had lied about his true identity.

Trenneborg had drugged the strawberries with the powerful sedative, Rohypnol. He marked the drugged ones by drawing on the stem leaves, so he knew which ones to present to his victim and which ones to eat himself.

After a while, the woman began to feel drowsy, before she fell unconscious. Once she was immobilised, Trenneborg raped the woman, before finding a wheelbarrow and placing her in it. He then pushed the wheelchair to his car which was parked outside. He lifted the woman out of the wheelbarrow and then bundled her into his car.

From here, Trenneborg drove the woman 350 miles to his home at Kristianstad. He had brought along two rubber masks – one of an elderly man and another of a bearded man. He had put one of these masks on his victim and one of the masks on himself to conceal their identities.

Trenneborg had been preparing for this moment for quite some time. Over the course of the past five years, Trenneborg had been building a hidden bunker which was concealed as a machine shed next to his countryside home.

Sweden's Josef Fritzl - Martin Trenneborg
Trenneborg’s home and bunker. Credit: Johan Nilsson/TT via Associated Press

The bunker was made from concrete and had walls that were one foot thick and double metal doors. The 600 sq ft bunker had a kitchen, bathroom and bedroom.1 The bunker even had a courtyard, so that the woman could go outside to get some fresh air without arousing suspicion.2

When the woman woke up, she was in an unfamiliar place. She recollected: “When I woke up, I had two needles stuck in my arms. He was sitting on a chair beside the bed.” Trenneborg drugged her with soporific to keep her sedated and then tested her for sexually transmitted diseases. He forced her to take a contraception pill, and over the course of the next six days, he held her captive in his bunker, sexually assaulting her when he pleased.

Trenneborg threatened that if the woman attempted to leave, he would leave her “a stinking corpse.” He also went into lurid detail, telling the woman exactly what he had done to her while she was unconscious. He also confided in her that he was going to abduct another woman to bring to the bunker. She later recollected: “He was targeting some kind of celebrity. Then he said that perhaps my mum could be the other girl in the bunker.”3

During the woman’s ordeal, Trenneborg drew up a list of sexual demands which included penalties if these demands were refused. Refusing sex was to be punished by adding 100 days to the woman’s captivity. An escape attempt would be punished by five more years. One year off could be earned by regularly performing certain sex acts or by taking part in a fitness program.4

A couple of days after the abduction, Trenneborg returned to the woman’s flat in Stockholm to collect some items. While in Stockholm, he discovered that the woman’s family had reported her missing. He noticed that the locks on the front door had been changed.5

Trenneborg panicked. He returned home and drove the woman to Stockholm police station. He told her to assure police that she was fine and that she had run away to be with Trenneborg, but while here, one of the police officers became concerned for the woman’s safety. He pulled her over to the side, and she quickly revealed the truth.6

When Trenneborg was arrested, evidence was uncovered that indicated that he was intending on keeping his victim prisoner for several years. Even more chilling, he had built the bunker for more than one victim. He admitted to drugging, kidnapping and holding the woman against her will, but he denied that he had raped her. He wanted his lawyer to try and get the kidnapping indictment refused to a less serious charge of “deprivation of liberty.”

When the terrifying case was reported in the media, many compared it to the case of Josef Fritzl, who held his daughter, Elisabeth Frtizl, captive for 24 years.

Sweden's Josef Fritzl - Martin Trenneborg
Martin Trenneborg

Trenneborg was ordered to stand trial for his crimes. His defence attorney said in the media that her client was a very unhappy person and that he was lonely. She said that he had no girlfriend and built the “property” to bring a woman “who was to be his girlfriend.” Defence attorney Mari Schaub said: “He wanted to live with someone.”

While the victim was pleased that Trenneborg was going to be facing justice with the upcoming trial, she had been struggling mentally, and knew that the trial would bring up bad memories of what happened to her.

The victim’s lawyer, Jens Högstrom, commented: “She has been treated for post-traumatic shock disorder. Now when the trial is coming up, her symptoms have escalated. She is having nightmares that remind her about the time she was in the bunker. A brief noise or sight, anything that reminds her of those days can put her in a terrible condition. But she is determined to get through the trial and then try to get on with her life.”7

Martin Trenneborg was ultimately found guilty of the abduction but was acquitted of aggravated rape because of lack of proof. The court had found that he had meticulously planned the woman’s abduction and had subjected her to serious risk by sedating her and keeping her locked up. Trenneborg was sentenced to ten years in prison.8

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  1. The Sun, 17 January, 2016 – “KO’s with Rohypnol Strawbs”
  2. EuroNews, 18 January, 2016 – “Trial of Doctor Accused of Drugging, Raping and Locking Victim in Bunker”
  3. The Times, 22 January, 2016 – “Swedish Fritzl Was Planning New Abduction, Claims Victim”
  4. The Times, 26 January, 2016 – “Swedish Fritzl Prepared Sex Contract”
  5. The Dominion Post, 23 January, 2016 – “Bunker Kidnap Victim”
  6. The Daily Telegraph, 22 January, 2016 – “Twisted Kidnap Doctor’s Sick Plan”
  7. The Gold Coast Bulletin, 22 January, 2016 – “Sex Slave trial to Begin”
  8. Associated Press, 23 February, 2016 – “Swedish Court Gives Doctor 10 Years for Abducting Woman”


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2 years ago

Wow!! Htf did he get off of the rape charges!??! I cannot believe that he only got 10 years for what he did to that poor woman. This sick fuck deserves to locked up for life!! The justice system is a complete joke!! Thanks for the share Emily!

2 years ago

The court was willing to accept the victim’s testimony regarding the kidnapping and imprisonment, but not the rape? That’s disgusting. There was certainly no justice here.

2 years ago

10 years is NOT enough!!
I only find SLIGHT solace in the fact that he was caught pretty quickly and unable to harm any other women. I feel so terrible for her though…. even a handful of days with that monster was enough to scar her for life. I really hope she can heal.

Julie Glosser
Julie Glosser
1 year ago
Reply to  Heather

Especially since he threatened to make her mom the other woman sick man

1 year ago

It didn’t mention if this beast lost his medical license but if he didn’t this is even worse!

1 year ago

Not enough!!! He will do it again!!! Keep him inside

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