When the use of cash bail ends across the state of Illinois this month, it will mean the end of a lengthy period of speculation, doomsaying and hope, and the start of the much drier work of putting the law into action.

The historic change has been more than two years in the making. It’s been the subject of fierce debate among politicians, academics and the general public, whose fears have been stoked by, among other things, a viral meme incorrectly claiming the new law will make all crime legal.

Starting on Sept. 18, judges will no longer be allowed to require people accused of crimes to put up money to leave jail while they await their trials. Instead, a judge will only be able to hold someone pretrial if they believe the person is likely to try and flee or pose a public safety risk.

It’s a huge change that will reshape courtrooms, jails and policing. On the cusp of this massive reform, here are five things to know.

1. The jail population is expected to shrink, but also change.

According to researchers at Loyola University, nearly 200,000 people are held in county jails throughout Illinois each year. Most experts expect the jail population to significantly decrease across the state. That’s because the law sets a higher bar for who can be held in jail while they are awaiting trial and judges won’t be able to keep someone just because they can’t afford bail.

But it’s possible defendants of some crimes may actually be more likely to be held in jail. For example, people accused of domestic violence are often given the option of cash bail in the current system, and the amounts can be relatively small. That means if they can afford to pay bail, they can walk free. But domestic violence charges often raise clear safety concerns, so it’s possible judges may hold more of these defendants in jail. A study from Loyola University researchers found that people arrested for domestic violence charges are likely to make up a large portion of people charged with “detainable” offenses.

2. Smaller counties may struggle under new procedural burdens.

The new law requires more robust courtroom hearings to decide if a person is held in jail. Those hearings will require more time from defense attorneys, prosecutors and judges. Many experts also predict that without the cudgel of pretrial detention, fewer defendants will strike plea deals, which will mean more resource-intensive criminal trials.

“It is going to be a real issue in some of the smaller counties,” DuPage County State’s Attorney Bob Berlin warned.

Advocates for bail reform have suggested counties take resources saved from the decreased jail population and put them toward courtroom operations.

3. Policing will change, too.

While courtroom operations and jails have been the focus of discussions around the Pretrial Fairness Act, the reform will also change how policing works in the state.

Under the law, police won’t usually arrest people for low-level misdemeanors like trespassing. Instead, they will give the person a ticket, and that person will get a date to appear in court in the future.

Police can still use discretion to take someone to jail if they pose a safety risk, continue to break the law after receiving a citation or lack proper ID.

4. There may be more legal actions ahead over the law.

The big decision is over — the Illinois Supreme Court deemed the new law constitutional earlier this summer, in response to a lawsuit brought by prosecutors from across the state, who claimed the legislative effort to end cash bail was an unconstitutional overreach. Sarah Staudt, an attorney with the Illinois Network for Pretrial Justice, said the language of the court’s decision is fairly direct and explicit. She also points to work done in the Legislature to clarify aspects of the bill some lawmakers found confusing.

But Staudt said “any law when you implement it and it’s a big new law, there will be questions of interpretation and different courts will interpret things different ways.”

For example, judges will still be exercising discretion in determining who meets the standards for being a risk to public safety. Those choices could be challenged, leading to court battles.

5. Other states will likely be watching for lessons.

Illinois is the first state in the nation to entirely eliminate cash bail. As the debate over bail continues to rage in other states, it’s likely people from both sides of the conversation will look to Illinois to prove their point.

People who support cash bail warn the change will lead to an increase in crime, including a Chicago Police union that said in court filings, “less detention results in more crime, including violent crime.”

Even those opposed to cash bail acknowledge there will be some instances of people released pretrial going on to commit other crimes. But those advocates also point to data that show that when Cook County drastically limited its use of cash bail in 2017, it “was not associated with any significant change in new criminal activity, violent or otherwise.”

That’s why cash bail opponents are hopeful Illinois will embolden reforms in other states. Insha Rahman, vice president at the Vera Institute, a national organization that works to end mass incarceration, said she believes the data from Illinois will prove “we can have both safety and justice.”

Shannon Heffernan reported this story for WBEZ’s criminal justice desk. Follow her @shannon_h.