As a defense attorney, there is nothing more challenging than a case where the client confesses to the crime. When a defendant confesses, juries almost always return a guilty verdict. It's easy to understand why: why would someone admit to something that could land them in prison unless they truly did it? This line of reasoning is so compelling that it's easy to assume that only the guilty confess, but the reality is far more complicated than that.
Innocent and sane people have been known to falsely confess, far more often than most people would ever imagine. A recent study found that of the three to eleven people conclusively proved innocent by DNA evidence, over 25% had given false confessions.
Why do innocent people confess? One reason is police interrogation techniques, which can be incredibly persuasive and can lead to false confessions. If you're interested in learning more about this topic, I highly recommend reading the article "The Interview" from The New Yorker (http://www.newyorker.com/magazine/2013/12/09/the-interview-7) which delves deep into the psychology of police interrogations and why they can produce false confessions.
In short, while it may seem like a confession is the smoking gun that proves guilt, it's important to remember that false confessions do happen, and that innocent people can be convinced to admit to crimes they didn't commit. As a defense attorney, it's my job to dig deeper and make sure that my client's rights are protected and that the truth comes to light.