(ATLANTA) — In charging former President Donald Trump and 18 co-defendants in a sprawling 41-count indictment, Fulton County District Attorney Fani Willis reached for a familiar legal tool.

From prosecuting school teachers to street gangs, it has not been uncommon for Willis to rely on Georgia’s Racketeer Influenced and Corrupt Organizations (RICO) Act throughout her career — but this time the former president is a remarkably uncommon defendant.

“It lets you get the big fish by working from the bottom up, by kind of indicting the whole pond,” Atlanta defense attorney Tom Church, who is not involved in the DA’s case, told ABC News.y

Since taking over as Fulton County district attorney, Willis has praised the versatility of the statute to “tell the whole story of a crime,” and by her own reckoning has pursued an unprecedented number of cases using the law. Two years ago she also tapped John Floyd, a seasoned lawyer who literally wrote the book on Georgia state RICO laws, to assist in the Trump probe, signaling how she might pursue the case.

Separate from the 1970 federal RICO law that precipitated the prosecution of some of the largest organized crime families, Georgia’s RICO law broadly mirrors the federal law with notable changes that broaden state prosecutors’ ability to charge defendants, according to multiple legal experts who spoke with ABC News.

Why does Georgia have its own racketeering law?

The federal RICO law originated from the concern that criminal organizations could not only inflict more harm on communities than individuals but were also harder to prosecute, according to Georgia State University College of Law professor Clark D. Cunningham.

“They felt that going after individual offenders was a little bit like that game of gopher, where you knock one thing down and another one pops up,” Cunningham said.

As federal prosecutors made strides against organized crime, state legislatures took note and began drafting state versions of the law. Georgia enacted its own law in 1980.

To be charged with a RICO offense in Georgia, a defendant needs to have allegedly committed or conspired to commit two related crimes — called racketeering or predicate acts — often as part of a larger criminal scheme, according to Chris Timmons, a trial attorney who spent 17 years trying RICO cases as a prosecutor with the DeKalb and Cobb County district attorney’s offices.

Georgia’s law permits prosecutors to charge as few as one defendant in a criminal scheme and does not require an extended timeframe for the crime, according to Timmons — giving prosecutors more leverage against individual actors.

“Somebody could go to JC Penney, shoplift a pair of socks, walk next door to Sears and shoplift a second pair of socks, and they can be charged with RICO,” said Timmons.

However, most RICO cases relate to broader schemes with multiple defendants. As a result, prosecutors tend to follow a similar approach to building a case.

“You work up the food chain,” Cunningham explained. “You start with people fairly far down … and so you have a lot of leverage to get cooperation.”

How have prosecutors used the RICO laws?

In the years following the passage of the federal and Georgia RICO laws, Georgia prosecutors began using the law to pursue cases against public officials, Cunningham said.

In 1984, prosecutors charged Georgia’s labor commissioner and multiple labor department employees with racketeering. Prosecutors eventually convicted the labor commissioner on fraud conspiracy charges.

As the federal law developed during the 1990s, Floyd began refining the Georgia law through multiple notable cases.

When Richard Hyde, then a Georgia state investigator, was considering how to prosecute fraud at the Medical College of Georgia in 1996, he turned to Floyd after reading about the lawyer’s unique approach to racketeering fraud. Describing Floyd as a “scary smart” yet “unassuming” lawyer, Hyde credited Floyd with helping successfully convict two faculty members who prosecutors alleged stole $10 million in research funds.

“He’s the only lawyer I wouldn’t want to ever be on the other side of,” said Hyde.

In 2002, Floyd successfully helped convict former DeKalb County Sheriff Sidney Dorsey on murder and racketeering charges after Dorsey ordered the murder of a political opponent who beat him in a 2000 election.

In 2014 and 2015, Floyd and Willis notably worked together in the RICO prosecution of 35 educators who engaged in a scheme to change test scores within the Atlanta public school system. The eight-month trial eventually resulted in convictions for 11 of the 12 defendants.

“He explained Rico in such a simplistic way that, you know, an 8-year-old would have been able to understand it,” said Clint Rucker, who tried the Atlanta public school case with Willis and Floyd.

Rucker said Floyd’s “laser-sharp” analysis and “professor-like” understanding of RICO not only helped the Fulton County DA figure out how to bring RICO charges in that case but also convinced the jury to convict on those charges, according to Rucker.

Floyd rejoined the Fulton County district attorney’s office in 2021 as an adviser in the Trump probe.

What challenges might arise in a racketeering case?

In recent years, federal prosecutors used the RICO statutes in notable cases including against former Detroit mayor Kwame Kilpatrick, and against some defendants in the so-called “Varsity Blues” case involving bribes to coaches and other officials at elite universities.

Some RICO cases require proving that the defendant stood to benefit by gaining money or property — which might present a challenge in the Trump case, according to Thomas.

“Here it’s not about money; it’s about power,” Thomas said.

Additionally, while RICO charges give a prosecutor the ability to describe a larger picture of criminal activity, describing that activity to a jury takes time.

The Atlanta public school case took eight months to try, on top of a six-week jury selection period.

“I would not be surprised if they were close to that same timeframe for the Atlanta public schools case,” Rucker said of the timeline for the Trump case, adding that jury selection for the former president’s case could be particularly challenging.

And to successfully convict, the prosecutors need to assemble the equivalent of a puzzle box of evidence to prove beyond a reasonable doubt that the defendants engaged in criminal activity.

“What a RICO prosecution does is it takes a lot of different pieces, odd shapes, different colors that may not seem to have any relationship with each other,” Cunningham said. “If the prosecution is successful, the jury says, ‘Oh my God, I see the picture … I see a vast conspiracy here."”

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