Like many, we're obsessed with true crime. Our favorite subject has to be serial killers. It's very morbid, but that's why we can't help but be fascinated by it. What would drive someone to do something so horrific. We're sure you know all the most famous murderers: Bundy, Dahmer and Gacy. But here's one that you likely have never heard about. That's right, even the most avid true crime lovers aren't aware of this notorious phantom...

The main focus of this story takes place in Heilbronn. Heilbronn is the sixth largest city in Germany and has approximately 123,000 citizens. And in the late 2000s, police investigators theorized that one of these citizens was a serial killer.

This killer was dubbed "The Phantom Of Heilbronn." They were known as a phantom because police had very little to go on when it came to their crimes.

All they knew about the Phantom is that they were prolific and well-traveled. DNA evidence from the Phantom was found in Austria, France and Germany from 1993 to 2009.

The Phantom's DNA was found at the site of 40 crimes. These crimes ranged from burglaries to murder.

The Phantom was linked to six murders. One of these victims was police officer Michèle Kiesewetter. She was killed in Heilbronn on April 25, 2007.

With one of their own among the victims, the Heilbronn police were out in full force to find this killer. This monster had alluded them and been a ghost for 14 years at this point. Could they find him?

Actually, we should clarify something. The Phantom of Heilbronn wasn't a "he." That's right: it was a female killer.

Female serial killers are exceedingly rare. With so little evidence to go on, the reward to find the murderer was increased to €300,000 in January of 2009.

Despite all the DNA evidence from the same woman found at so many crime scenes, some investigators started to suspect they were chasing a literal ghost. They felt that the Phantom of Heilbronn might not exist at all.

In March of 2009 while investigating a murder victim, police found the Phantom's DNA. When they looked into it, they made a discovery that took their search into a completely different direction.

It turned out there was no female Phantom killer at all. All of the DNA evidence was contaminated. What happened?

The cotton swabs the police used to collect DNA evidence were all contaminated, and not certified for human DNA collection. They all came from the same factory, and employed women who matched the Phantom's DNA. The swabs were contaminated before shipping, leading to the results to seemingly all come from one woman.

Because of this massive mishandling on the factory's part, in 2016 the International Organization for Standardization created new standards that would "[Minimize] the risk of human DNA contamination in products used to collect, store and analyze biological material for forensic purposes."

Now that the police were no longer chasing an imaginary killer, they were able to refocus their efforts and solve these now known to be unconnected crimes. Officer Michèle Kiesewetter's were found in 2011, and that case was finally closed.