Manfred Seel lived in Schwalbach am Taunus, a town in the Main-Taunus district of Hesse west of Frankfurt. He died in August 2014, aged 67. Reports from May 2016 gave cancer as the cause of death. The Hessian State Criminal Police Office, the Landeskriminalamt or LKA, described him afterward as a completely law-abiding citizen who had never come to the attention of the police. He had a daughter, and a firm bearing his name operated in the town. He has been described as a musician and as a gardener. The detective who presented the case for the LKA, Frank Herrmann, said that without the events that followed his death Seel would have been remembered as an ordinary family man.
His year of birth, schooling and work history are not on record.
In the weeks after his death, members of his family were settling his affairs. On September 10, 2014, a discovery connected with premises he had rented in Schwalbach was reported to the police. It concerned the death of a woman, and it led at once to a homicide investigation. The woman was later identified as Britta Simone Diallo, who had lived in Frankfurt.
The dead man could not be questioned and could not be tried. The inquiry therefore turned to older unsolved cases in Frankfurt and, later, to the public for information about his contacts.
The inquiry did not become public at once. On December 14, 2015, the dpa agency reported that the Frankfurt prosecutor's office had said several older cases were being reopened because of the discovery. A prosecutors' spokeswoman, Nadja Niesen, said that most of the possible victims came from one part of Frankfurt and that the number of cases involved was not yet known. A working group of the LKA called "Alaska" was checking whether the dead man could be tied to other unsolved killings.
In mid-May 2016 the LKA presented its findings at a press conference at its headquarters in Wiesbaden. Accounts differ on the exact day of the conference. The LKA named Manfred Seel, published his photograph, and appealed to the public for information. It asked about his contacts, his military service and training, his workplaces and the business he had run with a partner. It also asked friends and relatives of the women to come forward. The LKA stated that murder does not lapse under German law and that his death did not end the investigation. The LKA said there was a high probability that the death found in 2014 had been preceded by other killings.
The LKA's head, Sabine Thurau, was careful about the legal position. She said that no charge could be brought against the dead man and that he could never be convicted of murder in a court. The suspicion, she said, would stay a suspicion, and the presumption of innocence applied beyond his death.
The LKA's questions to the public named four women: Gudrun Ebel and Hatice Erülkeroglu, who died in 1971 in Frankfurt, Gisela Singh, who died in 1991, and Dominique Monrose, who died in 1993. Britta Simone Diallo, the woman identified after the 2014 discovery, was the fifth. The Associated Press reported on May 18, 2016, that police were checking whether four other deaths of women between 1971 and 1993 were linked to the same man, besides the death reported in 2014.
The figures given differed during 2016. t-online reported on May 20, 2016 that investigators believed he was responsible for at least six killings, with many more cases under review, and that a death around 2004 was among those examined. An interview published by web.de the same day also spoke of six. The Abendzeitung reported that two unsolved cases from 1998 and 1999 might be connected. The English-language site The Local reported that police believed him responsible for up to ten deaths. None of the numbers came from a court finding.
Investigators also raised the possibility that he had an accomplice in at least one of the cases. How many people were involved is not on record.
One case drew separate attention. In 1998, Tristan Brübach, a 13-year-old boy from Frankfurt, was killed in the city. The case has never been solved. In May 2016 the police said, according to the Associated Press, that features of the 1998 case suggested a possible link to the Schwalbach inquiry, while t-online noted that the boy did not fit the profile of the other victims.
The Frankfurt public prosecutor's office spoke again about the case later. In March 2023, t-online reported that the prosecutors' spokeswoman, Nadja Niesen, said a new line of inquiry examined about three years earlier had produced no concrete suspicion of a perpetrator. The same article named Seel among suspects who had been checked in the past years. It gave no date or result for that check, and it cited no evidence tying him to the boy's death. A police spokesman, Patrick Rüter, said that there had been no promising tips for some time. The file was dormant but could be reopened, and a reward of 20,000 euros remained on offer.
No charge, court finding or closing decision about Seel is on record. In May 2016 the inquiry was described as continuing, and a telephone line was open for tips. In October 2025 the Berliner Kurier reported that five killings were attributed to him and four further cases remained unresolved, and added that the total number was unclear and that the link to many of the cases had not been conclusively shown. No formal closure of the inquiry is on record.
Every killing attributed to Seel is an allegation made by the police after his death. He was never questioned, and no court has tested the evidence. The counts given vary: five, six, ten and "ten or more." The link to the death of Tristan Brübach was examined in 2016 but has not been shown, and the Frankfurt prosecutors said in 2023 that no concrete suspicion of a perpetrator had arisen. Whether he had an accomplice remains open. His occupation is given in more than one way.
The Seel case became a subject of television and film. In October 2025 the Berliner Kurier reported that the Frankfurt Tatort episode "Dunkelheit," shown on Das Erste, was based on the case. A ZDF documentary on the case was published on October 5, 2025. In 2016 the LKA asked anyone who had known the women it named to contact investigators; nothing further about their families is on record.
1971: Gudrun Ebel and Hatice Erülkeroglu die in Frankfurt; the LKA later names both in its inquiry.
1991: Gisela Singh dies; the LKA names her in its inquiry.
1993: Dominique Monrose dies; the LKA names her in its inquiry.
1998: Tristan Brübach, 13, is killed in Frankfurt; the case remains unsolved.
August 2014: Manfred Seel dies at age 67.
September 10, 2014: a discovery reported to the police leads to a homicide inquiry.
December 14, 2015: Frankfurt prosecutors confirm that several older cases are being reopened; the LKA group "Alaska" is at work.
Mid-May 2016: the LKA names Seel publicly and appeals for information; its head says he can never be charged or convicted.
March 2023: Frankfurt prosecutors say a review of the Tristan Brübach case about three years earlier found no concrete suspicion.
October 5, 2025: a press report says five killings are attributed to him and four cases are unresolved.