The news: In January, law enforcement officials announced that a crackdown on sex offenders who failed to register their address with police led to 40 arrests.

Behind the news: It is against Illinois law for child sex offenders to live within 500 feet of schools, playgrounds or any facility providing programs to children. Yet, as of Feb. 1, 29 child sex offenders in Cook County were breaking the law by living next to 34 Chicago Public Schools, shows a Chicago Reporter analysis of data from the Illinois Sex Offender Registry. The 34 schools were clustered primarily on Chicago’s South and West sides.

“This is the type of thing that can catch people off-guard,” said Sean Black, communications coordinator for the Illinois Coalition Against Sexual Assault. “It’s upsetting that these offenders slipped through the cracks.”

Offenders who are noncompliant with the law face mandatory fines, jail time and felony charges for repeat violations. Among the 29 violators were two child murderers and 10 sexual predators, while others were convicted of crimes such as kidnapping, sexual assault and child pornography. The U.S. Marshals Service declined to release the names of the 40 people it arrested during its eight-week investigation, and it is unclear whether the arrestees included any of the 29 violators near schools.

Debbie Cunningham, a sociology professor at Eastern Illinois University, suggested that sex offenders re-entering the community should be thoroughly assessed for their potential threat to children. Not all sex offenders “are at a high risk to reoffend–” they’re not all perverts–”but anytime somebody doesn’t follow the rules, it makes them a risk,” she said.