The Zodiac killer kept the country on edge for five years in the late 1960s and early 1970s before his series of murders in Northern California's Bay Area stopped abruptly. The killer was never found, though plenty have speculated on his identity.

Now the FBI could be only a positive forensic test away from solving the mystery, according to a report by CBS13.com in Sacramento.

The TV station says an FBI source confirmed that the agency is running lab tests on some items suspected of being linked to the killer.

It's hardly the first potential break in the case — evidence and suspects have come and gone with no resolution — but Dennis Kaufman, who provided the FBI with the new evidence, thinks he has the answer.

"The identity of the Zodiac killer is Jack Tarrance. He's my stepfather," Kaufman told CBS13.com.

Jack Tarrance, who was born in 1928 and died in 2006, served in the Air Force and Navy and worked variously for General Electric, a steel company and a laundry, according to "America's Most Wanted."

The FOX TV show's Web site says that he wasn't identified as a suspect until 2000, when Kaufman dug up and revealed clues that seemed to point to his stepfather as the killer.

Click here for more on the story from CBS13.com.

Click here for more from America's Most Wanted.