I'm against the death penalty, but literally anyone can claim the evidence critical for sentencing was faulty in any crime. The article also says that the defense "sought" DNA evidence as a reason for delaying the execution, but this was a 23-year-old crime, so the odds of new DNA evidence turning up are effectively zero--and the defense knows that, so they could play this card to get an indefinite delay even if that DNA, if discovered, would actually further establish guilt.
Abolish the death penalty. Even if this guy was truly guilty, killing him didn't bring anyone else back.