When repeat drunken driver Donald Canterbery killed a Granite City couple this year, his case left authorities expressing not only anger, but also embarrassment.

After all, Madison County prosecutors admitted, they had cut Canterbery a lenient plea deal on a DUI charge just a month before the crash. They said they thought it was his first one - unaware that he had four other drunken-driving cases from four states.

Despite the fatal mistake, Illinois authorities aren't trying to figure out how many other repeat offenders got plea deals meant for first-timers.

And authorities won't help the public figure it out, either - even though what little data are available show the problem is not isolated.

The Post-Dispatch tried to find out how often Illinois courts gave repeat offenders a deal called court supervision - which is probation without a DUI conviction. That's what Canterbery got.

Madison County Circuit Clerk Matt Melucci keeps court data that could be studied, but his office said it was so busy it did not provide data to the public, no matter the topic.

Illinois Secretary of State Jesse White keeps similar data, but White's chief deputy, Thomas Benigno, said releasing it would violate federal law. That's despite the law allowing research on public safety - the reason Missouri released its data on drunken drivers.

White's office eventually agreed to release data on a fraction of drunken drivers who may have been arrested in Missouri and Illinois. Out of 1,603 such drivers, the newspaper found at least 47 cases of people convicted for DWI in Missouri and then given court supervision in Illinois. That includes 25 people in Madison and St. Clair counties.

But because of the limited data released, that number is probably just a fraction of repeat offenders who have benefited. Without more cooperation from authorities, there's no way to quantify how many more.