For starters, 96% of those cases on the site occurred prior to the 00's. Forensics have improved rapidly since then, but of course is still not perfect. Really life isn't CSI after all.
Not to mention, if you weigh up the number of cases that go unsolved versus those committed wrongly, it's probably in the 0.000X%.
Look at all of the homicides that go unsolved every single year. Now compare them to advanced cities like London, where Cameras line the streets. London has more people living in a higher density (more chance of crime), than almost every single American city combined. Yet, their homicide rate per capita is a fraction of Chicago.
I remember seeing a guy beaten and robbed during the protests in London. The cameras recorded the incident and the dirt-bag was caught and he was charged.
No chance in hell would he have been caught in most of our dilapidated cities, as there isn't the means there to find and convict them. It's why gangs and organized crime are so rampant, in every single one of our cities.