What can truly be known?

Without dabbling into philosophical ideas of how nothing is truly known because of a "brain in a vat" theory, it can still be said that nothing, no matter how certain or guaranteed is truly known. There are ways to fool the eyes, the mouth, the ears, the nose, and even our sense of feeling without the use of a hypothetical electrical stimulation in a simulated world, and thus there is a way to fool the mind of what it believes is knowledge. Because of this, is there any way to be certain of what one knows?
One argument against this is that if one claims to have done something they should not have, and they have no signs of mental instability, their statement is truth. Otherwise there would seem to be no reasoning behind such a confession.
Sadly, this has proven to not be the case. Multiple times there have been confessions proven to have been false confessions. As reported in the Texas Death Penalty Blog, Max Soffer has been sitting on death row for thirty years because of a false confession, and he has not received an opportunity to prove his true innocence in this time. This man has already, in essence, lost his life due to a mistake.
There is already at least one occurrence of a wrongful conviction resulting in a wrongful death. Deathpenaltyinfo.org reports that Cameron Willingham was sentenced to death for killing his three children in a fire, and years after he was executed, it was found that the trial was horribly flawed and that it is extremely unlikely that he performed any of the actions he was sentenced for.
It's awful enough that anyone should be found wrongfully guilty of any crime, but for even one life to be killed for it is inexcusable. At least with a life sentence, there is an opportunity to increase certainty and save more innocent lives and insure that the true murderer is found, because even in the most solid case, nothing is certain.

Texas Death Penalty Blog
http://texasdeathpenalty.blogspot.com/2010/03/aclu-asks-supreme-court-to-review-case.html

Death Penalty Info
http://deathpenaltyinfo.org/ongoing-investigation-texas-execution-throws-new-doubt-defendants-guilt