It is said that the tapes never lie. Sometimes, though, they get doctored. Or they are so garbled that they don't appear to be much help at all.

Take, for instance, the eavesdropping device the FBI slipped into the Branch Davidian compound in Waco, Texas, in 1993. The transmitter recorded the final moments of the cult members who perished in the conflagration that destroyed the compound,

Almost as soon as the fire was extinguished, there was a question that would have implications all the way to Oklahoma City: Did the cult members start the blaze, or did the government?

Authorities turned to the recordings for answers. But the tapes were virtually indecipherable. There were explosions and gunfire. The people inside the compound spoke through gas masks that muffled their voices.
The transmitter itself was of not very good quality.

So federal authorities did what they have been doing for years when faced with a situation like this: They called on Paul Ginsberg, of Spring Valley, N.Y., perhaps the nation's foremost expert in enhancing, cleaning up, and authenticating audio and video recordings.
"I think he's the best in the country," said former Bergen County Prosecutor John J. Fahy, who worked with Ginsberg as prosecutor and when he was with the U.S. Attorney's Office. "He's an incredible technician, the best audio guy I've ever met."

Ginsberg, 52, has earned his reputation through two decades of work on more than 1,500 cases. He has participated in a number of important federal cases, including the World Trade Center bombing and the standoff at the Branch Davidian compound in Waco. He is still examining videotapes of the White House coffee sessions that are at the center of the investigation of Democratic Party fundraising activities in 1996.

Ginsberg has also participated in high-profile state-level criminal trials. He has aided in the prosecution of a number of New Jersey organized crime figures. Ginsberg found an additional 22 minutes of recording made by Kathleen Weinstein, the special-education teacher from Tinton Falls who was carjacked and murdered in Toms River in 1996. Weinstein taped the final moments of her life as she tried to persuade her captor to release her.

In December, Ginsberg helped prosecutors rebut an ill-prepared expert in the felony murder trial of Patrick J. Pantusco, the Washington Township man accused of leading police on a pursuit that ended in the death of an Oradell woman. Pantusco was later convicted.

Ginsberg is also expected to testify at two upcoming trials of significant local interest. The engineer will likely testify about an answering machine recording of a phone message Wyckoff teenager Brian Peterson left for girlfriend Amy Grossberg shortly after the teens allegedly dumped the body of their newborn baby in a trash bin in a Delaware motel in November 1996. That trial is expected to begin in May.

Ginsberg also is expected to give testimony at the federal trial of three Palisades Park police officers accused of running a burglary ring from 1991 to 1995. A number of secret tape recordings of those ,officers were made by an officer wearing a concealed microphone. That trial is expected to begin this month.

The unassuming engineer has top-secret federal clearance as a result of his work on the World Trade Center case, where he worked to clean up surveillance tapes made by an undercover informant. He attends holiday parties at the Justice Department and rubs elbows with U.S. attorneys.

Ginsberg's work, though, is so widely praised that he is often called upon by defense attorneys.

"My credibility is everything," Ginsberg said. "I call it the way I see it."

He has worked on a number of civil cases as well, including the custody battle between Woody Allen and Mia Farrow that involved accusations that Allen abused the couple's daughter, Dylan.

In that case, Ginsberg testified on Allen's behalf about a videotape made by Farrow in which dylan described the alleged abuse. Ginsberg said the tape was recorded at a number of different times, opening up the possibility that the child was coached. Allen won the case.

Ginsberg came upon his life's calling quite accidentally. While working in the mid-1970s to build a recording studio for a planned National Lampoon radio show, Ginsberg got a call from the U.S. Attorney's Office in Newark. The federal prosecutors were preparing to prosecute a number of developers involved in the notorious plot to bribe former Fort Lee Mayor Burt Ross and another borough official to help obtain zoning approvals for a $250 million plaza planned near the George Washington Bridge.

Ross, working with investigators, taped a number of conversations in which he bargained over the amount of the bribe he would receive. But the tapes were of poor quality, and former U.S. Attorney Jonathan L. Goldstein asked Ginsberg to help.

At first, the engineer was reluctant. That was before a contract was put before him.

"As soon as I saw how much it was for, I asked to use the phone," said Ginsberg. "I called my wife to tell her I was in a new line of work."

The work, Ginsberg says, can be immensely satisfying. Ginsberg designs and builds some of his own

equipment. Hehas access to all of the latest surveillance devices and is occasionally asked to lecture federal agencies, such as the Secret Service, on how to properly keep an eye on someone.

Ginsberg is almost never told about the entirety of a case when he is asked to work on a recording. Sometimes the recording is peripheral to the case and he finds out about it only afterward, in the newspapers.

Sometimes, though, the tape is the case. The FBI wouldn't turn over their World Trade Center surveillance tapes until Ginsberg finished building a special evidence safe for that case.

"I love my work," he says. "I really get to make a difference."

The Waco case was one of the more storied and difficult of Ginsberg's career. Ginsberg set to work in his Spring Valley laboratory, painstakingly eliminating the noises that interfered with the recorded speech of the cult members.

Eventually, Ginsberg was able to make the tapes clear enough so that jurors considering the criminal charges against the surviving cult members could hear the voices of the Branch Davidians as they planned to set the compound ablaze. Discussion about a common camping fuel were most helpful, the engineer said.

"We were able to show the jurors that the fires were set from within, and not as a result of government action," Ginsberg said.