PORTLAND, Ore. (KOIN) – An amateur D.B. Cooper investigator plans to sue the Federal Bureau of Investigation because he thinks he may have found a key to solving the case.

D.B. Cooper investigator Eric Ulis wants to examine the hijacker’s tie because investigators may have missed a feature that could contain DNA. 

Ulis says he discovered a spindle in a tie “precisely like DB. Cooper’s,” that rises up. Ulis says he talked to previous D.B. Cooper FBI investigators who told him they didn’t realize the tie has the adjustable spindle. 

KOIN 6 News interviewed Ulis who’s traveling to Washington D.C. to file a federal lawsuit under the Freedom of Information Act on Wednesday to try to force the FBI to allow him and a DNA expert to examine the tie, then use genetic genealogy.

The FBI already has obtained a DNA sample on D.B. Cooper.

“The partial DNA profile that the FBI has is from the tie. It is unclear as to where on the tie it came from. Given that it was 2001 and we’re dealing with 2001 technology, they probably pulled something off of the front of the tie from the fibers, maybe a little bit of saliva that was dried up or something of that nature.”

Ulis is hoping examination of the spindle would lead to a complete DNA profile.

“We actually do possess the technology, the ability to pull the smallest amounts of DNA off of metal and these types of things,” said Ulis.

Ulis told KOIN 6 the FBI recently denied his request to examine the tie under the Freedom of Information Act, which is forcing him to file the lawsuit.

“They’ve given access to the tie two separate times before to private scientists, private individuals, once in 2009 and once in 2011, and this could actually solve the case.”

“That gives us the ability to take D.B. Cooper’s DNA and sort of reverse engineer this and identify his family, nephews, nieces, people of that nature,” Ulis said.

In November, Ulis announced he had focused on a man named Vince Petersen as a D.B. Cooper suspect after tracing a rare chemical previously found on the tie to a lab where Peterson worked near Pittsburgh, Pennsylvania.

New analysis points to Vince Petersen as a suspect in D.B. Coopers infamous skyjacking (Eric Ulis)

Solving the case is up to amateur sleuths since the FBI announced in 2016 it was no longer investigating the 1971 DB Cooper hijacking at Portland International Airport.

In a statement to KOIN 6 News, the FBI said it does not comment on potential litigation.