PROVIDENCE — When Andrew F. Merola and Nicholas S. Pari were charged with assassinating Joseph P. “Joe Onions” Scanlon 30 years ago, their lawyers cried foul. In arguments before and during their trial, and again after a jury convicted the men of first-degree murder, the defense attorneys tried to derail the prosecution.

“The state has no body, no weapon, no bloodstains, no scientific evidence, no physical evidence,” Merola’s lawyer argued to the jurors.

But even though the state could not produce a body to prove that Scanlon was dead, prosecutors had a live witness –– Scanlon’s girlfriend –– who testified that she had watched Merola fire a handgun into the back of her lover’s head while Pari diverted his attention by punching him in the face.

They also had another witness, who said he helped Merola wrap Scanlon’s body in plastic garbage bags and place it in the trunk of Merola’s car. Then there was the FBI informant from Brooklyn, N.Y., who told the jury that Merola came to his home and told him he had killed Scanlon because he was a “stool pigeon.”

Jurors interviewed after the trial said they found the testimony convincing. After nearly six hours of deliberation, they pronounced both defendants guilty “beyond a reasonable doubt.”

Years later, after their convictions were overturned based on errors made by the trial judge, Merola and Pari admitted killing Scanlon. As part of a plea agreement, the now-deceased Merola pleaded no contest to second-degree murder and was sentenced to serve 10 years of a 25-year term. Pari was ordered to serve 7 years of a 20-year sentence for manslaughter.

While the Joe Onions case was the first murder prosecution in Rhode Island where no body had been recovered, there have been nearly 300 of them in the United States dating to the 1800s. And most of the prosecutions have resulted in convictions.

Washington, D.C., lawyer Thomas A. “Tad” DiBiase –– who spent more than 12 years as an assistant U.S. attorney prosecuting mostly homicide cases –– keeps track of all of the “no body” cases in the United States as a hobby. His Web site –– www.nobodycases.com –– lists all of the “no body” trials ever held.

One of the first, in 1843, involved three men accused of murdering the master of their schooner, the Sarah Lavinia, on the “high seas” off the coast of New England. But most such prosecutions have been in the last 30 years. According to DiBiase’s research, as of Nov. 13 of this year, there had been 279 “no body” murder trials in the United States and the Virgin Islands, and only 25 of them had resulted in acquittals or had been overturned on appeal.

DiBiase said in an interview yesterday that he believes there are just three states ––Vermont, New Hampshire and Idaho –– where prosecutors still haven’t tried a “no body” case.

One of the most high-profile cases now being played out on the nightly news is a “no body” case in Florida. Casey Anthony, 22, is facing a first-degree murder prosecution and a possible death penalty in the disappearance of her toddler daughter, Caylee Anthony.

Bloody carpeting, broken eyeglasses, strands of hair, dentures, tooth fragments, a bloodied hatband, a bullet hole in a missing person’s winter coat. These were the key pieces of evidence that have linked defendants to murders in some of the “no body” prosecutions throughout the country. In some of these cases, like the “Joe Onions” murder case, there is also eyewitness testimony. But often it was just circumstantial evidence that led to convictions.

DiBiase, who prosecuted a “no body” murder case in the District of Columbia in 2006, won a second-degree murder conviction against a man who allegedly shot and killed his girlfriend during an argument in their home, even though none of the five children who were home at the time witnessed the killing and the victim’s body was never found.

While some prosecutors may be loath to take them on, DiBiase asserts that “no body” cases often aren’t all that hard to win. If there isn’t good forensic evidence, often a suspect will confess to the police or “it’s a case of friend rats on friend. … A lot of these cases are not stranger-on-stranger crimes but usually a husband killing a wife or a boyfriend killing a girlfriend. The second most common type is parents killing children or in some cases, strangers killing children. Typically, the first “no body” cases were those where ships would come back without a captain or a first mate because they’d been thrown overboard. The murder trials that followed were against crew members.”

In an interview yesterday, former Rhode Island Attorney General Dennis J. Roberts II said that “some of the people in my office thought I was crazy to base my decision to present the [Joe Onions] case to a grand jury on the testimony of a hooker. But I thought she was a credible witness.” And, he pointed out, “we got convictions” and Merola and Pari both served substantial time in prison.

tbreton@projo.com