We always ask ourselves: Do the facts add up? Or are there logical inconsistencies?

Evidence is far from being proof. It has to be understood in context with all of the other results of an investigation.

DO INANIMATE OBJECTS HAVE FINGERPRINTS?

The crime scene techs examine the body for evidence. They apply about 150 pieces of sticky tape to the body from head to toe, pull them off, and send them to the lab. There forensic specialists place the pieces of tape under a microscope and inspect the 5,000 to 10,000 fibers on each strip for foreign material. That results in a highly reliable list of everyone who has come into close contact with the victim. But the search for footprints in the condo produces less reliable information: “The floor is as clean as a whistle—as though it had just been scrubbed,” explains Inspector Ogait. “The only footprints were those of the paramedics.” Investigators use light of varying intensity and wavelength to make footprints visible. By shining the light at an extremely acute angle, they can even see the shadows cast by extremely fine dust particles.

Now the search for the possible murder weapon begins. It leads the investigators to a hatchet in one of the kitchen cabinets. At first there are no signs of fingerprints or blood—but something else makes things seem suspicious. The hatchet’s head looks like it’s the same size as the wound. Forensic examination performed by a pathologist reveals the truth: “The doctor has measured the length of the victim’s skull fracture—it’s exactly the same as the back of the hatchet head,” says Ogait. So the victim was killed in the bathroom, and the culprit then tried to conceal the evidence.

The course of events is clear—and now the perpetrator must be found. Fingerprints left in the condo point to two suspects, and investigators have already questioned them both. The first suspect is Arne Dugan, an unemployed neighbor of the victim: “We knew each other quite well. I’d often drop by for a cup of coffee or tea—and three days ago I sat with her for about an hour. Louise worked as a freelance artist and we always ran into each other in the hallways. My condo is right below hers.”

The second on the list is Bernhard Cohen, an art dealer. He doesn’t deny having visited Barr: “I looked at her new paintings, and we had a cup of coffee together. I’m always searching for new work to display in my gallery.” The fingerprints in the living room and the kitchen, some of them on glasses, bottles, and even on a painting, match up with his testimony. But what about the fibers found on the victim’s body? Both suspects acknowledge having hugged the victim, which may explain the fibers. The only difference: Fibers from Cohen’s clothing were primarily found around the victim’s shoulders and chest, while those from Dugan’s clothing were found on her back—an inconsistency. So what conclusions should you draw as an investigator?

“An embrace would leave fibers in the shoulder area and perhaps on the front of the torso,” says Ogait. “Fibers on the back suggest a struggle, or that the body was dragged from one place to another.” Forensic techs also found flakes of Dugan’s skin on Barr’s back. “Every one of us loses around 30,000 skin cells per hour,” explains Superintendent Stresemann. “And the DNA from just one of them is sufficient for making a positive identification.”

IS THERE SUCH A THING AS THE PERFECT MURDER?

Okay, for an expert this murder was a relatively easy exercise, but: “It was realistic, nevertheless,” says Ogait. “Perpetrators will often panic and try to destroy evidence and create new evidence in the process.” The perfect murder would have to be disguised as the perfect accident: “Sometimes a murder will go undetected by the medical examiners, and they don’t call us in,” says Ogait. If all the signs point to a natural cause of death, the “murder van” stays in the garage. But Ogait offers little hope for potential killers: “If there is even the slightest indication that a cause of death was deliberate, we get to work with every tool available to us—and believe you me: We have a lot more weapons in our arsenal than you’ve seen here.”