Sgt. Todd May of the state police special investigation support unit said he and others in the department specialize in the investigation of murders and complex cases.
From time to time, old cases are reopened, May said. Sometimes new evidence comes to light but other cases are looked at again just to see if investigators can come up with something. The Zimmerman case is one of three unsolved murders in Washington County handled by the Maryland State Police.
"Over the past year, Sgt. Ronald Cullison and I have conducted more than 100 interviews and developed new leads," May said.
In addition, the state police crime lab has reviewed all the physical evidence with new technology, such as DNA testing. It's possible that evidence could now be used for comparison purposes, May said.
"The information developed in the investigation indicates the (killer) was in all likelihood a member of the community and may have been known to Lori," May said.
He also believes there are people in Hagerstown who have information and haven't come forward, either because they are afraid or are reluctant to get involved.
"It is our hope that anyone who believes they have information about this case would call and help bring closure to this tragedy for the sake of Lori's family," May said.
Zimmerman's partially clad body was found on Reno Monument Road south of Boonsboro on April 14, 1984 - several days after the 15-year-old South Hagerstown High School student had been reported missing by her mother.
According to police reports, Lori had been severely beaten but the official cause of death was asphyxiation. There was no official determination of sexual assault, police said.
A nearby resident found her body in a wooded area under large pieces of cardboard that were weighted down with rocks.
Police said all along they didn't believe Lori was murdered at the site where her body was found.
For months after, police tried to reconstruct Lori's movements. She was last seen in downtown Hagerstown by a relative on April 6, 1984.
The trail soon cooled.
Four years later, then-lead investigator Sgt. Keith Wattenschaidt, now retired, participated in a segment of "Unsolved Mysteries," the television show hosted by actor Robert Stack.
On film, Wattenschaidt met with psychic Dorothy Allison in a last-ditch effort to turn up a suspect.
Contacted this week, Wattenschaidt said Allison came pretty close to where police found Lori's body.
"But she really didn't come up with much we could use about the killer's profile," Wattenschaidt said.
Anyone with information can call state police in Hagerstown at 301-739-2101 or the MSP support unit at 1-410-290-0050.