From years of dealing with home invasion specialist Frank Zuccarello, Broward's top homicide investigator is convinced he is a habitual liar, ``an untrustworthy witness who should not be believed under oath or otherwise.''

Broward Sheriff's Office Maj. Tony Fantigrassi said so in a sworn affidavit.

But that same Broward Sheriff's Office used Zuccarello's testimony to put a man on Death Row.

The BSO homicide unit is now under fire. Several cases are under review after DNA evidence exonerated a Death Row inmate who died of cancer while awaiting execution.

Among them is the case of Michael Rivera, who was put away with the assistance of Zuccarello. An admitted flasher who fancied wearing women's clothing, making obscene phone calls and accosting young girls, Rivera found himself in jail at the same time as Zuccarello.

Rivera's attorney says Zuccarello, now 36, was a key witness in the 1987 trial. Rivera was charged with killing 11-year-old Staci Jazvac, who was pulled from her bicycle, murdered and dumped in a field.

Zuccarello buoyed the case with his story of a jail-cell confession. The well-spoken felon stands by his story.

``Why would he say he did it if he didn't?'' Zuccarello said. ``He was a sick individual who said he killed that little girl and a jury of his peers found him guilty. I would testify again, if I had to.''

Fresh doubts about Zuccarello's testimony have Rivera's lawyers bombarding the courts with petitions for a new trial and for DNA testing on a hair sample from Rivera's van. A DNA test would prove whether the hair came from Staci's head.

``It is quite disturbing that you have a situation where someone in the Broward Sheriff's Office is acknowledging that Zuccarello cannot be trusted to tell the truth,'' said Marty McClain, a Death Row attorney representing Rivera. ``And yet they let him take the stand and used him to help send Michael Rivera to death.''

Sheriff's officials declined to discuss the Rivera case, citing the ongoing DNA probe.

``It wouldn't be appropriate for us to discuss details of this case until the review is complete,'' said spokeswoman Cheryl Stopnick.

Stopnick said BSO detectives take care when using information from jailhouse witnesses.

``We always will listen to whatever anyone has to say, but we're always extremely cautious and careful with information we get from someone who is in jail,'' Stopnick said. ``Many times people in jail would like to cut some kind of a deal or make a bargain.''

Fantigrassi met with Miami-Dade prosecutors in 1989 to voice concern about Zuccarello and eventually signed an affidavit stating he had ``serious doubts about the claims that Frank Zuccarello made'' in an unrelated Dade murder case. The affidavit was dated Feb. 4, 1999, more than 10 years after Rivera was convicted. But it referred to events as early as 1984.

Prosecutors downplay Zuccarello's role in Rivera's case.

``I think I'd have convicted him without the three jailhouse people,'' said Kelly Hancock, a former prosecutor now in private practice, of Zuccarello and two other prison witnesses. ``I did not think Zuccarello was my main witness in that case.''

In April 1986, Rivera and Zuccarello shared a cell at the Broward jail. Zuccarello was charged with home invasion robberies, Rivera with exposing himself and the attempted rape and murder of an 11-year-old Coral Springs girl.

Rivera soon found himself facing an even more serious charge. Staci Jazvac disappeared on Jan. 30, 1986, while riding her bike to the store to buy school supplies in Lauderdale Lakes. Her body was found 15 days later in a field in Coral Springs.

Apart from Zuccarello's testimony, there was not a lot to link Rivera to the murder -- except a rambling, unrecorded statement made to detectives over a period of several days.

Zuccarello, then a personable, 22-year-old felon, gave some of the most dramatic testimony in the Rivera murder trial. With every answer on the witness stand, he tied up another loose end in the prosecution's case.

He testified that Rivera confided in jailhouse conversations that he had abducted Jazvac ``to fondle her, to molest her'' and had choked her to death when she struggled.

Zuccarello, reached last week at his home, said he can hardly remember the trial.

``I can't say if he was guilty or not,'' Zuccarello said. ``I don't know if he really did it or not or if he was fantasizing and getting his jollies when he told me what he did.''

Some veteran investigators say the Rivera testimony was a familiar ploy for Zuccarello, a man known for leading police to other criminals and, in turn, getting reduced sentences.

Zuccarello was charged with 23 felonies, including home invasions, armed robberies and kidnappings, when he met Rivera. He was sentenced to five years on a plea agreement and got out of jail after 2 1/2 years. ``He knew the system and was playing the system,'' said Steve Emerson, a special agent with the Florida Department of Law Enforcement who knew Zuccarello, speaking to The Herald in 1999.

Zuccarello admitted during an unrelated murder trial in Miami that he enjoyed a special relationship with Miami police -- they had taken him out of jail so he could attend a Dolphins game, get haircuts and visit his girlfriend's house, where detectives waited outside while Zuccarello and his girlfriend had sex.

Fantigrassi, then a BSO homicide detective, met Zuccarello while investigating the 1984 murder of Charles Hodek, who was discovered slumped over the steering wheel of a car with three gunshots to the head in South Broward.

The Hodek investigation went nowhere until 1986. But the tide turned when Zuccarello was booked into the Broward County Jail as a suspect in a string of home invasion robberies. Zuccarello quickly gave up his pals -- a gang of thugs who ripped off drug dealers in their own homes after threatening to shoot their genitals.

Then Zuccarello started talking about two other murder cases: Hodek and Stanley Cohen, a wealthy developer from Coconut Grove.

Zuccarello claimed to know who had killed Hodek. But Detective Fantigrassi said Zuccarello's statements didn't ring true and, in 1988, Zuccarello admitted to lying and falsely implicating a suspect in the 1984 Hodek murder.

Zuccarello also implicated two men in the well-publicized 1986 Cohen murder. Cohen was shot while sleeping in his home March 7 of that year.

For months, Zuccarello traveled back and forth between Broward and Miami-Dade counties meeting with detectives and prosecutors on the Hodek, Cohen and Rivera cases. During one jaunt to Miami-Dade, Zuccarello flunked three Miami police lie detector tests about the sequence of events the night Stanley Cohen was shot. Four weeks later, he would tell Broward cops that Rivera had admitted killing Staci Jazvac.

Fantigrassi tried to discourage prosecutors from using Zuccarello as a key witness in the Cohen trial, but prosecutors still did.

Only Fantigrassi knows why he felt strongly enough to send the 1999 affidavit regarding Zuccarello's role in the Cohen case. Fantigrassi did not return several phone calls. Colleagues say he is known as a fastidiously ethical cop.

Defense attorneys say the Zuccarello saga underscores a larger problem.

``I think it's almost a given that snitches are used to get convictions, particularly in cases that are weak,'' said Barbara Heyer, a Broward County criminal defense attorney.

The only significant physical evidence prosecutors presented during the Staci Jazvac trial was a sample of dirty blond hair found on the bed of a van Rivera sometimes drove. A BSO forensic expert said it could have come from Staci Jazvac, but maybe not.

The strongest testimony came from Detective Thomas Eastwood, who administered more than a dozen polygraphs to Rivera over an eight-hour period. Eastwood said the polygraphs were inconclusive.

Between polygraph exams, Eastwood said Rivera told him, ``Every time I get into a vehicle, I do something terrible.''

According to Eastwood, Rivera then confessed to a different crime -- the attempted rape/murder of the 11-year-old girl in Coral Springs -- and began to cry.

``Tom, I can't stop myself,'' Rivera said, according to Eastwood. ``I can't control myself. Either kill me or put me in jail because I'm going to keep on doing what I'm going to do if you don't stop me.''

Zuccarello was one of three jailhouse witnesses who testified at Rivera's trial.

A fellow prisoner named Peter Salerno testified that Rivera told him, ``I didn't mean to kill the little Staci girl . . . I just wanted to look at her and play with her . . . I seen her on a bike and she excited me.''

Another cellmate, Bill Moyer, testified that Rivera confided to him in jail that his alter-ego, ``Tony,'' had killed Jazvac.

Their testimony was of questionable worth.

Salerno had testified as state's witness in at least 10 other trials.

Moyer, who testified he was speaking out of concern ``for my children and everybody else's children in the world,'' was being held for sexual battery on his stepdaughter.

The rest of the case hinged largely on crank calls Rivera placed to local women.

Starr Peck, his former boss, testified that Rivera, posing as `Tony,' told her by phone, ``I've done something very terrible. I killed her and I didn't mean to.''

But some details didn't match the facts. Rivera told Peck he had dumped Staci's body by Lake Okeechobee. The body was found in Coral Springs.

The defense contended no evidence firmly tied Rivera to the crime.

But when the weeklong trial was over, on April 16, 1987, the Broward jury found Rivera guilty of the Jazvac slaying.

Its unanimous vote two days later: Rivera should die.