Hinterkaifeck was a small farmstead situated between the Bavarian towns of Ingolstadt and Schrobenhausen, approximately 70 kilometres (43 mi) north of Munich. On the evening of March 31, 1922, the six inhabitants of the farm were killed with a mattock. The murders remain unsolved.
The six victims were parents Andreas Gruber (63) and Cäzilia (72); their widowed daughter Viktoria Gabriel (35); Viktoria's children, Cäzilia (7) and Josef (2); and the maid, Maria Baumgartner (44).
Hinterkaifeck was never an official place name. The name was used for the remote farmstead of the hamlet of Kaifeck, located nearly 1 kilometre (0.62 mi) north of the main part of Kaifeck and hidden in the woods (the prefix Hinter, part of many German place names, means behind), part of the town of Wangen, which was incorporated into Waidhofen in 1971.
A few days prior to the crime, farmer Andreas Gruber told neighbours about discovering footprints in the snow leading from the edge of the forest to the farm, but none leading back. He also spoke about hearing footsteps in the attic and finding an unfamiliar newspaper on the farm. Furthermore, the house keys went missing several days before the murders. None of this was reported to the police prior to the attack.
Six months earlier, the previous maid had left the farm, claiming that it was haunted; the new maid, Maria Baumgartner, arrived on the farm on the day of the attack and was killed hours later.
Exactly what happened on that Friday evening cannot be said for certain. It is believed that the older couple, as well as their daughter Viktoria, and her daughter, Cäzilia, were all lured into the barn one by one, where they were killed. The perpetrator(s) then went into the house where they killed two‑year‑old Josef, who was sleeping in his cot in his mother's bedroom, as well as the maid, Maria Baumgartner, in her bedchamber.
On the following Tuesday, April 4, neighbours came to the farmstead because none of its inhabitants had been seen for a few days. The postman had noticed that the post from the previous Saturday was still where he had left it. Furthermore, young Cäzilia had neither turned up for school on Monday, nor had she been there on Saturday.
Inspector Georg Reingruber and his colleagues from the Munich Police Department investigated the killings. More than 100 suspects have been questioned throughout the years, with the most recent questioning taking place in 1986. None of the questioning yielded any results.
The day after the discovery of the bodies, court physician Johann Baptist Aumüller performed the autopsies in the barn. It was established that a mattock was the most likely murder weapon. Evidence showed that the younger Cäzilia had been alive for several hours after the assault — she had torn her hair out in tufts while lying in the straw, next to the bodies of her grandparents and her mother. The skulls of the corpses were sent to Munich, where clairvoyants examined them, to no avail.
The police first suspected the motive to be robbery, and they interrogated travelling craftsmen, vagrants, and several inhabitants from the surrounding villages. This theory was abandoned when a large amount of money was found in the house. It is believed that the perpetrator(s) remained at the farm for several days – someone had fed the cattle and eaten food in the kitchen, and the neighbours saw smoke from the chimney during the weekend – and would have easily found the money if robbery had been the intention.
The death of Karl Gabriel, Viktoria's husband (who had been reported killed in the French trenches in World War I), was called into question. His body had never been found. However, most of his fellow soldiers reported seeing him die, and the police believed their reports.
Two-year-old Josef was rumoured to be the son of Viktoria and her father Andreas, who had an incestuous relationship that was documented in court and known in the village. A neighbouring farmer named Lorenz Schlittenbauer publicly claimed to be Josef's father, and paid alimony to Viktoria and Andreas. Shortly before the murders, Viktoria was preparing to sue Schlittenbauer, who by then had a wife and a baby, for alimony. Schlittenbauer was part of the original search party that found the corpses, and he disturbed the bodies before the police arrived. The police questioned Schlittenbauer extensively but were unable to find concrete evidence linking him to the crime.
In 2007, the students of the Polizeifachhochschule (Police Academy) in Fürstenfeldbruck examined the case using modern criminal investigation techniques. They concluded that it is impossible to definitively solve the crime after so much time had passed. The primitive investigation techniques available at the time of the murders yielded little evidence, and in the decades since the murders, evidence has been lost and suspects have since died. Despite these setbacks, the students did establish a prime suspect, but did not name the suspect out of respect for still‑living relatives.
The six victims are buried in Waidhofen, where there is a memorial in the graveyard. The skulls were never returned from Munich, after having been lost during the chaos of World War II.
The farm was demolished a year after the attacks, in 1923. Close to where the farm was located, there is now a shrine.