Where's Baby Sabrina?

Troy Roberts Reports On One Family's Search For Their Daughter

(CBS)  The indictment is based on the secret police bugging operation that lasted nearly three months. Those bugs recorded more than 2,600 conversations between the Aisenbergs in which police say they discussed killing their daughter.

Prosecutors say these taped conversations proved that Steve had killed their daughter.

"I thought, ‘The government has a hell of a powerful case here,’" says Fitzgibbons.

At the couple's bail hearing, a federal prosecutor told a judge she had heard Steve on tape saying, "I wish I hadn't harmed her. It was the cocaine.”

"I'll do drug tests from now to eternity, and you’ll never find any drugs in my system," adds Steve. "I never said anything that they say I said. Marlene never said anything that they said she said."

But do the tapes contain a confession, or will they just add to the confusion already surrounding the case?

It's been more than two years since Sabrina vanished from her crib. And federal prosecutors were sure they had a case, not a murder case, but a case of conspiracy.

In December 2000, the Aisenbergs were about to have their day in court. The audiotapes were the backbone of the prosecution's entire case. But people in the courtroom said it was very difficult to understand the tapes.

"I later described it as it sounding like chickens squawking with a hurricane playing in the background," says Brink. "It was just noise."

"All we could hear in the courtroom that day was mumbling. And you could hear the hum of appliances," adds McGinty. "When it was played in open court and the judge looked over at the prosecutor, and that look was a glare, 'This is the best you got?'"

Cohen hired a former analyst from the FBI to listen to the tapes. To combat Cohen's expert witness, Kunz hired celebrity private investigator Anthony Pellicano, whose clients included Michael Jackson and Liz Taylor.

Pellicano had a reputation for resorting to violence to get his way, and he later pleaded guilty to possessing illegal explosives. "Why would the government stoop to hiring Tony Pellicano, when shortly after that, he was indicted himself, and he's in federal prison today?" asks Cohen.

It appeared that Pellicano and the prosecutors were the only ones in the courtroom who could hear the incriminating evidence, and this came as no surprise to the Aisenberg team.

48 Hours hired its own audio expert, Jack Mitchell, to listen to the tapes. "It's almost as if it were just simply made up," says Mitchell, who has worked for the U.S. Department of Justice. "There is no evidence whatsoever on any of these recordings that I have examined that will implicate the Aisenbergs in the disappearance of baby Sabrina. None."

Mitchell has analyzed hundreds of tapes during his career, and is convinced that some of these voices may not even belong to the Aisenbergs.

48 Hours also played the tape to Perros, who could not understand any of the evidence. "It sounds like they had some type of technical problem with the application," says Perros.

The damning evidence was nowhere to be found. "All lies, just all lies. We knew there was nothing on those tapes," says Marlene.

All of this was enough to make Cohen suspect the worst: that the Aisenbergs were framed. "They wanted a quick confession, clear this case, and look good," says Cohen. "But the only problem was they didn't have any facts, so they had to make them."

The prosecution's case against the couple began collapsing. Now, it was the feds who had some tough questions to answer.

In fact, two judges appointed to review the prosecution's case found the Aisenberg tapes were "largely unintelligible." They called some of the statements false, and pure fiction. In a stunning blow to the prosecution, the recordings were ruled inadmissible.

One week later, all charges were dropped.

After repeated calls to Kunz were not returned, 48 Hours approached him for answers. He refused to comment.

While it was a hollow victory for the Aisenbergs, they have never given up. Today, they hope a new clue will bring their daughter home.

To this day, the Aisenbergs keep a separate bedroom in their Maryland home reserved just for Sabrina, even buying her souvenirs from their vacations.

They believe Sabrina is somewhere alive and well, and is being raised by a family who desperately wanted a child. At times, Sabrina’s return has seemed tantalizingly close.

But Marlene has good reason to never give up hope. In May 2003, a couple in Illinois began adoption proceedings on a 6-year-old child, Baby Paloma, who did not have a birth certificate. The Aisenbergs were hopeful, and Pontiac Police Chief Don Scholsser began an investigation.

A lot of people, including the Aisenbergs, believed the mystery behind Sabrina’s disappearance was about to be solved. "It all just seemed like it was gonna fit, and that this could really be her," says Marlene. "We were on pins and needles, on edge, just praying it was gonna be her."

For two weeks, they waited for the results of a DNA analysis. But Paloma’s DNA did not match. Paloma's natural mother was a Mexican woman who abandoned her baby at a clinic on the Texas border. A nurse at the clinic gave the baby to her sister in Illinois. Eventually, the sister adopted Paloma legally.

Are the Aisenbergs still angry? "If they bring Sabrina home, I won't be angry, and I have to pray that they will do the right thing, that they will look for her and bring her home," says Marlene.

These days, the Aisenbergs put their hope in those who’ve stood by them; the staff at the National Center for Missing and Exploited Children has been invaluable.

Joe Mullins is a forensic artist at the center who creates age-progressed photos of what children may look like years after they’ve gone missing. This technology has helped in the recovery of more than 500 children.

Using facial features from Sabrina’s older brother and sister at about the same age, Mullins created an image of what Sabrina might look like today at 7.

"I pray to God somebody can look at her and say, 'That's an Aisenberg,'" says Marlene. "I believe that she could herself see this picture, and she's old enough to say, 'Oh my God, this looks like me.'"