The Murder of Lucie Trezzini

Who Lucie Trezzini was

Lucie Trezzini was 16 years old and came from the canton of Fribourg. In early 2009 she was living with a family in the canton of Schwyz, where she worked as an au pair. Her death that March became one of the most widely discussed criminal cases in Switzerland, and around 1,000 people attended her funeral.

What happened in March 2009

On 4 March 2009 Lucie was approached in Zurich by a man who presented himself as someone looking for young women to model for photographs. According to reports from the trial, he offered her 500 francs to pose for jewellery pictures. She went with him to his apartment in Rieden, a locality near Baden in the canton of Aargau, and he killed her there.

The man, identified in Swiss media as Daniel H., was then about 25 years old, an unemployed cook with a drug dependency. Several days later he went to the police, turned himself in and confessed. Lucie's body was found in his apartment. At trial he said he had lost his job and his girlfriend and wanted to go back to prison.

An offender already known to the authorities

It soon emerged that Daniel H. had a serious prior record. In 2003 he had attacked another young woman and nearly killed her, and he was later convicted of attempted murder. Instead of a standard prison term he was ordered in 2004 into a measure for young adults known as work education, and he spent about four years in a rehabilitation institution. He had been released on parole roughly seven months before Lucie's death.

Public anger focused on how a man known to have committed such a violent act, and who was using drugs and alcohol, could be at liberty apparently without adequate supervision. That question shaped both the court proceedings and the later political debate in Aargau.

The trials in Aargau

The case was tried by the Baden district court at the end of February 2012. Because of the strong public interest, the two-day hearing was held in the municipal hall of Untersiggenthal. Daniel H. admitted the killing and was convicted of murder. Reports differ on the prison term set at this stage: Swiss Italian broadcaster RSI and swissinfo reported a 20-year sentence, while SRF and Blick later described it as a life sentence. All agree that the court ordered ordinary indefinite detention (Verwahrung) but refused the lifelong form sought by the prosecution and supported by Lucie's parents, because the psychiatric experts did not consider him beyond all treatment.

Ordinary detention is reviewed periodically and can end in release if an offender is no longer judged dangerous. Lifelong detention, added to the Federal Constitution after a 2004 popular initiative and applied from 2008, is meant only for offenders considered permanently untreatable. Campaigners behind that initiative criticised the Baden verdict as ignoring the will of voters.

The prosecution and the family appealed. On 18 October 2012 the Aargau high court ordered lifelong detention. It found Daniel H. currently untreatable, noting that both experts saw little prospect of successful therapy for at least 15 years, and concluded that he was permanently untreatable.

The Federal Supreme Court ruling

The defence took the case to the Federal Supreme Court in Lausanne, arguing that the meaning of permanently untreatable needed to be settled. In December 2013 the court overturned the lifelong detention order. It held that the term means untreatable for the rest of the offender's life, and that the experts had only been able to predict failure of therapy for about 10 to 15 years. The case went back to Aargau, where the high court imposed ordinary detention alongside a life sentence. No party appealed again, and SRF reported in March 2014 that the judgment was final.

Under the life sentence, conditional release could not be considered before 15 years had passed, counting his time in custody since 2009. A court would also have to find a favourable prognosis, and SRF reported in 2014 that release appeared very unlikely.

Compensation, reforms and the offender's death

In August 2017 the canton of Aargau confirmed an out-of-court settlement with Lucie's parents. The amount was not disclosed; her father described it as partial compensation that did not cover the family's costs. The canton acknowledged organisational failings in how it had handled dangerous offenders and errors in applying the criminal code. After the killing, Aargau reorganised the enforcement of sentences and measures and placed its probation services under the cantonal administration.

On 21 December 2023 Daniel H., aged 40, was found dead in his cell at the Lenzburg prison in Aargau. The authorities said they presumed suicide and that there had been no earlier signs of suicidal behaviour. No later developments in the case were found in reporting from 2024 to 2026.

Why the case matters

The Lucie case became a reference point in Swiss criminal law because it forced the Federal Supreme Court to define what permanently untreatable means for lifelong detention, setting a demanding standard for that measure. It also exposed weaknesses in how early-released violent offenders were assessed and supervised, and it prompted organisational reforms in Aargau and a wider national debate about cooperation between courts, psychiatrists and probation services.