When most people hear about individuals who spent years or decades behind bars, they have the same assumption: That person must have done something awful to warrant such a lengthy imprisonment.

It certainly seems like a logical assumption, but recent studies show how wrong we are. Since 1989, there have been more than 2,000 people wrongly convicted of serious crimes. Each of them spent years behind bars for crimes they didn't commit.

Now, criminal defense attorneys in Milwaukee, prosecutors and advocates are searching for answers. How did so many innocent people end up behind bars, and what can we do to help ensure this doesn't keep happening?

The answers are alarming. Criminal law experts point to numerous errors leading to the exonerations. Police corruption led to wrongful arrests. In other situations, witnesses who could corroborate the stories of wrongly accused individuals backed out of their testimonies. Faulty eyewitness testimony and lying witnesses are also pervasive problems.

But there was also one cause that few people suspected. In numerous cases, innocent people admitted to crimes that they didn't commit -- crimes in which their names were completely cleared by DNA evidence. Experts believe that under persistent and prolonged questioning by investigators, some individuals believed they were doomed no matter what they said. In an effort to minimize their sentences, individuals confessed to crimes they didn't commit.

Although more than 2,000 wrongful convictions in 20 years is a staggering number, experts believe there are numerous other exonerations that still need to happen. For example, some of the largest cities and counties in the country reported no exonerations, while relatively small cities reported disproportionately high numbers.

What can we do to help ensure we do not continue putting innocent people behind bars?

Source: Los Angeles Time, "Registry tallies over 2,000 wrongful convictions since 1989," David G. Savage, Washington Bureau, May 20, 2012