Science crucial to cracking BTK case

After Wichita police arrested Dennis Rader in 2005, some people refused to believe he could be the so-called BTK serial killer.

To them, there was no way Rader, a by-the-book Park City animal control officer, could be the merciless killer who called himself BTK — for bind, torture, kill — who had haunted Wichita beginning in 1974. The Dennis Rader they knew was a devoted father and husband, a church president and a former Boy Scout leader.

But police had a powerful scientific tool — testing of DNA genetic material — that proved Rader was in fact BTK, police Lt. Ken Landwehr explained to listeners Monday night.

Investigators matched his DNA to his crimes in a creative way.

Without Rader's knowledge, police used a search warrant to obtain a sample from his adult daughter's pap smear, on file with a medical office.

As father and daughter, they shared genetic material.

The sample came back as a match to the BTK crime scene samples.

It proved she was the daughter of BTK.

Landwehr, the longtime head of the Wichita police homicide unit who led the BTK investigation, explained how the science of DNA testing is crucial to solving violent crimes.

Landwehr spoke during a gathering at the Donut Whole hosted by Science Cafe-Wichita, a program sponsored by Kansas Citizens for Science.

By early 2005, investigators were building a case against Rader because of his blundering communications with police before he was caught.

But the DNA evidence was crucial.

By the time of Rader's arrest, DNA testing had improved immensely, Landwehr said.

Such testing wasn't available during the earliest BTK crimes, dating to 1974.

"When Dennis Rader started killing, no police officer ever knew of DNA," Landwehr said.

"And fortunately for us, neither did Dennis Rader."

Over the years, investigators had collected items from the BTK crime scenes that would later be tested for DNA.

From 1974 to 1991, BTK murdered 10 people. Police obtained semen samples from two BTK crime scenes — near the bodies of 11-year-old Josephine Otero and 25-year-old Nancy Fox. They also found the killer's DNA under a fingernail of 28-year-old Vicki Wegerle. She had scratched her killer.

Monday night, when the audience got to question Landwehr, a woman at the back of the room told him: "I just want to tell you how grateful I am" — to him and other investigators —"for putting him behind bars."

This story was originally published March 15, 2011 at 12:00 AM with the headline "Science crucial to cracking BTK case."