Tristan Brübach

The police are certain that Seel murdered at least five women, and perhaps as many as nine – primarily sex workers, drug addicts and people suffering from mental illnesses – between 1971 and 2004.

Seel was considered a potential suspect primarily because he and Brübach lived in the same area, rather than there being any evidence linking him to Brübach's murder.

Brübach does not fit Seel's victim profile in terms of age and gender.

However, Seel did exhibit sexual sadism in his presumed murders and kept the genitals of some of his victims.

Tristan Brübach (3 October 1984 – 26 March 1998) was a 13-year-old German boy who was murdered in the Frankfurt suburb of Höchst.

His murder remains unsolved.

Tristan Brübach was born on 3 October 1984 in Frankfurt am Main to parents Iris and Bernd.

Iris committed suicide in 1995, leaving Bernd to raise Tristan alone.

Brübach grew up in Höchst and Unterliederbach, both suburban neighbourhoods on the outer fringes of Frankfurt.

He attended Walter Kolb Primary School in Höchst before going to secondary school in Sindlingen, another suburb of Frankfurt.

Tristan was described as shy but very streetwise, spending a lot of his free time walking around his neighbourhood with no specific purpose.

He was extremely fond of animals: despite his shyness in all other scenarios, he would regularly approach strangers of all ages who were walking their dogs, so that he could enter into conversation with them about their pets.

Brübach was last seen alive at Bruno-Asch-Anlage – a park in front of Frankfurt-Höchst railway station – at 3:20 pm on the day of his murder.

His body was discovered by children walking home from school.

They returned to the school to tell their teachers, and the police were informed at 5:08 pm.

Brübach's body was in a pedestrian tunnel that runs alongside an underground section of the Liederbach river; the tunnel is known locally as the Liederbach Tunnel.

Brübach had been beaten unconscious and strangled, though the cause of death was a long slash across his neck.

Both testicles, as well as flesh from his buttocks and thighs, had been removed.

The murder weapon lay on a concrete block nearby.

The murder had been seen from a distance by three teenagers (not the same people as the children who discovered Brübach's body); however, they did not realise at the time what they were witnessing.

These witnesses gave the police a description of the suspect and a composite sketch was produced.

In March 1999, a year after the murder, Tristan's rucksack was found in a forest in Niedernhausen, 25 kilometres (15 miles) from the crime scene.

The rucksack contained a Czech-language road atlas of Germany, which is believed not to have belonged to Brübach, who did not speak Czech and had no reason or means to possess such an item.

The police consequently expanded their enquiries to the Czech Republic and Slovakia, but no viable leads emerged.

A large-scale fingerprinting operation began in 2002.

All males aged between 15 and 45 from Höchst and Unterliederbach, as well as male commuters in that age bracket who used Frankfurt-Höchst railway station (Frankfurt's second busiest) at the time of the murder, have been invited to submit fingerprints samples voluntarily.

By 2014, 98.65% of 15-to-45-year-old males from Höchst and 92.95% of those from Unterliederbach had done so.

Among other false leads, an American woman told the police that her German ex-husband was the murderer.

However, she later recanted her accusation, admitting that she had made up the story to take revenge on her ex-husband after an acrimonious divorce.

Seel died in 2014 aged 67.

He lived a seemingly ordinary life, holding the same job for decades, raising a family, having no criminal record and being an active and respected member of his local community, among other things being in a jazz band.

However, after his death, his daughter was looking through his belongings in a rented storage facility and found human remains and diaries containing graphic descriptions and sketches of murders.

On 19 May 2016, the Hessen State Office of Criminal Investigations (Hessisches Landeskriminalamt) in Wiesbaden announced that Manfred Seel was being looked into as a suspect.

In October 2017, the press officer of the Frankfurt Police announced that Seel had been excluded as a suspect in Brübach's murder.

The prime suspect is a male aged between 20 and 30 with either a cleft lip or a large scar on his upper lip and of a generally unkempt appearance.

This man was seen by several people, all of whom contributed to drawing up the composite sketch.

The sketch was shared with law enforcement authorities worldwide, but no suspects matching the image have emerged.

The first person to see the suspect on the day of the murder was a 12-year-old girl walking through the Liederbach Tunnel, where Brübach would later be murdered.

The girl reported that she saw the man coming out from behind a bush.

He was wearing a hat, with a ponytail visibly dangling from the back of it.